The Cambridge Natural History Part 38

The Prairie-dog or Prairie-marmot is some 10 inches to one foot in length.

The tail is no more than 2 inches. The ears are very small; the thumb is fully developed and bears a claw. The measurements of the various sections of the intestine are the following:--Small intestine, 860 mm.; large intestine, 690 mm.; caec.u.m, 75 mm. Thus the caec.u.m is not large comparatively speaking. These animals dig burrows on gra.s.sy plains which they share with the Ground Owl (_Speotyto cunicularis_) and with Rattlesnakes, all three species appearing to live in perfect amity.

Probably the Owls use the conveniently-constructed burrows, and the Rattlesnakes come there to look after the young of both.

[Ill.u.s.tration]

FIG. 233.--Long-tailed Marmot. _Arctomys caudatus._ 1/7.

Closely allied to the last are the Marmots, genus _Arctomys_. They differ in the rudimentary character of the thumb and in the longer tail. The eyes and ears are small. The distribution of the genus is Nearctic and Palaearctic. There are ten species of {466} the genus. The Alpine Marmot, _A. marmotta_, is familiar to most persons. The animal lives high up in the Alps, and when danger threatens it gives vent to a shrill whistle. It hibernates in the winter, and as many as ten to fifteen animals may be found closely packed together in a single, carefully-lined burrow.

The only other European species is _A. bobac_, the Siberian Marmot, which occurs in the extreme east of Europe, and is also Asiatic. There are four North American species, including the Quebec Marmot, _A. monax_.

[Ill.u.s.tration]

FIG. 234.--Flying Squirrel. _Pteromys alborufus._ 1/5.

The genus _Pteromys_ (of which the proper name, antedating _Pteromys_ by five years, appears to be _Petaurista_) is confined to the Oriental region, where there are a dozen species or so. The limbs are united by a parachute extending to the toes, and supported anteriorly by a cartilage attached to the wrists. There are also membranes anteriorly uniting the fore-limbs to the neck, and posteriorly uniting the hind-limbs to the root of the tail and a trifle beyond. The skull and the dental formula are as in Sciurus, but the pattern of the molars, which is much complicated, seems to argue a different mode of nutrition. There are twelve pairs of ribs. The large intestine (in _P. petaurista_) is very nearly as long as the small, and the caec.u.m is also "colossal"; the measurements in an individual of the species named were: small intestine, 670 mm.; caec.u.m, 320 mm.; large intestine, 650 mm. {467} The caec.u.m is disposed in a spiral. The teats are three pairs, non-inguinal in position.

The size of these squirrels is 16 to 18 inches exclusive of the tail, which is longer. These animals can make an exceedingly long jump with the help of their flying membrane. Nearly eighty yards is the longest distance given for these aerial excursions. It is stated that they are able to steer themselves to some extent while in the air. As appears to be the case with so many Rodents, these animals feed largely upon beetles and other insects, besides bark, nuts, etc.

The allied genus _Sciuropterus_ has a much wider range. It extends into the Palaearctic region and into North America, besides being found in India.

There is here no membrane reaching to the tail. The palms and soles are furry. The caec.u.m is very much shorter, and so is the large intestine. The latter, in _S. volucella_, is not more than one-third of the length of the small intestine. In other features there are no remarkable differences in structure, save that the mammae, always three pairs, may be inguinal.

Of the genus _Eupetaurus_[336] but a single species is known, which is limited to high alt.i.tudes at Gilgit and perhaps in Thibet. Its princ.i.p.al difference from the other genera of Flying Squirrels is that the molars are hypselodont instead of brachyodont. The interfemoral membrane is rudimentary or wanting. The one species is _E. cinereus_. It is thought to live "on rocks, perhaps among precipices." Dr. Tullberg attributes the hypselodont teeth to the fact that the mosses upon which it is believed to feed may have much sand and earth intermingled, which would naturally lead to a more rapid wearing away of the teeth, and hence a need for a good supply of dental tissue to meet this destruction.

FAM. 3. CASTORIDAE.--This, the third family of the Sciuromorpha, contains but one genus, _Castor_, the Beaver, with at most two species, one North American, the other European. This large Rodent has small eyes and ears, as befits an aquatic animal, and the tail is exceedingly broad and covered with scales; the transverse processes of the caudal vertebrae, in order better to support the thick tissues lying outside them, are divided in the middle of the series into two. The hind-feet are much larger than the fore-feet, and are more webbed than in any other aquatic Rodent. {468}

In the skull the infraorbital foramen is small as in Squirrels. The pos...o...b..tal process has practically vanished. The four molars stand out laterally from the jaws. The incisors, as might be surmised from the habits, are particularly strong. The stomach has near the entrance of the oesophagus a glandular patch, which seems to be like that of the Wombat (see p. 144). In both s.e.xes the cloaca is very distinct and comparatively deep.

The two species of the genus are _C. canadensis_ and _C. fiber_. The latter is of course the European species, which is now found in several of the large rivers of Europe, such as the Danube and the Rhone. But it is everywhere getting scarce, and limited to quite small and isolated colonies.

In this country it is absolutely extinct and has been since before the historic period. There is apparently no doc.u.mentary evidence of its survival down to this period. But the numerous names of places which are called from this animal ill.u.s.trate its former prevalence. Examples of such names are Beverley in Yorkshire, and Barbourne or Beaverbourne in Worcestershire. In Wales, however, Beavers seem to have persisted longer.

But they were rare in the Princ.i.p.ality for a hundred years or so before the Norman Conquest. The king Howel Dda, who died in 948 A.D., fixed the price of a Beaver skin at 120 pence, the skins of Stag, Wolf, and Fox being worth only 8 pence apiece. The Beaver was called by the Welsh "Llost-llyddan,"

which means "broad-tail." Its existence in the country is handed down in the name of Llyn-ar-afange, which means Beaver lake. The last positive record of the Beaver in Wales seems to be the statement of Giraldus Cambrensis that in 1188 the animal was still to be found in the river Teivy in Cardiganshire. In Scotland the Beaver is said to have continued down to a later date. Ireland it never reached. The remains of this animal by their abundance show the former prevalence of _C. fiber_ in this country. It is known from the fens of Cambridgeshire, and from superficial deposits elsewhere. The Thames formerly had its Beavers, and apparently it was widely spread through the country generally.

The Beaver not only furnishes collars and cuffs for coats; it was used, as every one knows, to provide hats. But the usefulness of the animal by no means ended here in the eyes of our {469} forefathers. The Rev. Edward Topsell observed that "for giving great ease unto the gowt the skinnes of beavers burned with drie oynions" are excellent. Castorein as a drug, if not in actual use, has quite recently been a part of the pharmacopoeia. It is derived from the a.n.a.l glands common to this and other Rodents, and indeed many other mammals.

A large extinct form of Beaver is _Trogontherium_,[337] found in the "Forest-bed" of Cromer. The skull is about one-fourth longer than that of _Castor_. It has a less inflated bulla, and slightly more p.r.o.nounced pos...o...b..tal processes than _Castor_. The third molar (fourth grinding tooth) is relatively larger than in _Castor_, and has a rather more folded crown. The foramen magnum is more triangular.

FAM. 4. HAPLODONTIDAE.--A separate family seems to be required for the genus _Haplodon_, whose characters will therefore be merged with those of its family. It is to be distinguished from most other Squirrel-like creatures by the fact that there is no pos...o...b..tal process to the frontal.

The molar teeth are five in the upper and four in the lower jaw. The Sewellel, _H. rufus_, like the other species of the genus (_H. major_), is found in North America west of the Rocky Mountains. It has the habit of the Prairie-marmot, and has a short tail, only moderately long ears, and five-toed feet. Tullberg is of opinion that this animal nearly represents the ancestral form of the Squirrel tribe.

SECTION 2. MYOMORPHA.

This subdivision of the Rodents contains, according to Mr. Thomas's recent estimate,[338] no less than 102 genera. It is therefore obviously impossible to do more than refer to some of the more interesting of these.

This group is again divided into the following families:--

(1) Gliridae, including the Dormice.

(2) Muridae, the Rats, Mice, Gerbilles, Australian Water-rats, Hamster.

(3) Bathyergidae, Cape Mole, etc.

(4) Spalacidae, Bamboo Rats. {470}

(5) Geomyidae, Pouched Rats.

(6) Heteromyidae, Kangaroo Rats.

(7) Dipodidae, Jerboas.

(8) Pedetidae.

The Gliridae have no caec.u.m, so usual in the Rodentia. It is true that all the genera have not been dissected, but it is known that in the true Dormice, as well as in the genus _Platacanthomys_, a caec.u.m is absent.

Apart from these few exceptions the Mouse-like Rodents all possess a caec.u.m, though it is often not very large. They are all smallish animals, and are modified to a great variety of habit and habitat. There are burrowing, swimming, and climbing forms. The group is universal in range, even including the Australian region, in which they are the only Rodents.

FAM. 1. GLIRIDAE.--This family, also called Myoxidae,[339] includes the Dormice, and is entirely an Old-World family, absent only from the Malagasy region. Its most important differential character is the total absence of the caec.u.m and of any sharp boundary between the small and large intestine.

The molars are usually four. The eyes and ears are well developed.

The genus _Muscardinus_ includes only the Common Dormouse, _M.

arellanarius_. This small creature, 3 inches long with a tail of 2 inches, is, of course, a well-known inhabitant of this country. It is also found all over Europe. It is not particularly abundant in this country, and a good specimen is said to be worth half a guinea. As the specific name denotes, it lives largely on hazel nuts; but it will also suck eggs and devour insects. The animal makes a "nest" in the form of a hollow ball. Its hibernation is well known, and has also given rise to the German name ("Schlafer") of the group. It was well known to Aristotle, who gave or adopted the name [Greek: Eleios] for the animal. Its winter sleep--suggestive of death--and its revivification in the spring gave the Bishop of Salamis, Epiphanius, an argument for the resurrection of man. The fur was reckoned in Pliny's time a remedy for paralysis and also for disease of the ears.

The genus _Myoxus_ includes also but a single species, _M. glis_, the so-called "Fat Dormouse" of the Continent. It has no {471} glandular swelling at the base of the oesophagus, such as occurs in the last genus and in _Graphiurus_. Of _Graphiurus_ there are thirteen species, all African in range. The genus does not differ widely from the last. There is, however, a glandular region of the oesophagus. _Eliomys_ is the last genus of typical Dormice. It is Palaearctic in range.

_Platacanthomys_, of a Dormouse-like form, has like other Dormice a long tail, on which the long coa.r.s.e hairs are arranged in two rows on opposite sides towards the tip; it is represented by a single species, _P.

lasiurus_, from the Malabar coast. It is arboreal in habit. The fur is mingled with flattened spines. The molars are reduced to three on each side of each jaw. This form has been bandied about between the "Mice" and the "Dormice"; but Mr. Thomas's discovery of the absence of the caec.u.m argues strongly in favour of its correct location among the Gliridae. _Typhlomys_ is an allied genus, also from the Oriental region. This and the last are placed in a special sub-family of the Gliridae, Platacanthomyinae, by Mr.

Thomas.

FAM. 2. MURIDAE.--This family, that of the Rats and Mice in a wide sense, is the most extensive family of Rodents. In it Mr. Thomas includes no less than seventy-six genera. The molars are generally three. The tail is fairly long, or very long, and the soles of the feet are naked.

SUB-FAM. 1. MURINAE.--The true Rats and Mice may be considered to form a sub-family, Murinae. The genus _Mus_, including the Rats and Mice in the limited sense of the word, contains about 130 species. They are exclusively Old World in range, being only absent from the Island of Madagascar. In the New World there are no species of the restricted genus _Mus_. The eyes and the ears are large; the pollex is rudimentary, and bears a nail instead of a claw. The tail is largely scaly. All the members of the genus are small animals, some quite minute. In this country there are five species[340] of the genus, viz. the Harvest Mouse, _M. minutus_, which has a body only 2 inches long with an equally long tail. It is the smallest of British quadrupeds with the exception of the Lesser Shrew. The Wood Mouse, _M.

sylvaticus_, is about twice the size; it differs also from the last species in that it {472} frequents barns, and is thus sometimes mistaken for the Common Mouse, from which, however, it is to be distinguished by its coloration and longer ears. The latter, _M. musculus_, is too familiar to need much description. A curious variety of it has occurred. This has a thickened and a folded skin like that of a Rhinoceros, and the hair has disappeared. The Black Rat, _M. rattus_, is like a large Mouse, and is smaller and blacker in colour than the "Hanoverian Rat." It is sometimes called the "Old English Rat," but seems nevertheless to be not a truly indigenous Rodent. It has been so defeated by compet.i.tion with the Hanoverian Rat that it is now not a common species in this country.

The Hanoverian or Brown Rat, _M. dec.u.ma.n.u.s_, is a larger and a browner animal than the last. It is very widely distributed through the globe, no doubt largely on account of the fact that it is readily transported by man.

The same is the case with the Common Mouse, whose real origin must be a matter of doubt. The original home of the Brown Eat is thought by Dr.

Blanford to be Mongolia. There is so far a justification for the name "Hanoverian Rat" that the animal seems to have reached this country about the year 1728. But there is no reason for calling it, as is sometimes done, the Norway Rat.

Some members of this genus, whose fur is interspersed with spines, or which are quite spiny, have been separated as a genus, _Leggada_, which, however, is not generally allowed.

Closely allied again is _Chiruromys_, which has a strongly prehensile tail, a feature which is not common among the Myomorpha, though _Dendromys_, a tree-frequenting form, and _Mus minutus_, already spoken of, show the same character. Many Mice seem to have prehensile tails, which they can curl round branches; but it is not so fully developed as in the species just named.

A number of other genera are referable to the true Mice, the sub-family Murinae of Thomas's cla.s.sification. The Syrian and African _Acomys_ has very spiny fur, so much so that "when it has its spines erected it is almost indistinguishable at the first glance from a diminutive hedgehog."

The genera _Cricetomys_, _Malacomys_, _Lophuromys_, _Saccostomus_, _Dasymys_ are restricted to the Ethiopian region. _Nesokia_ is Oriental, reaching {473} also the Palaearctic region. _Vandeleuria_, _Chiropodomys_, _Batomys_, _Carpomys_ are Oriental, the last two being confined to the Philippines.

Another peculiar Philippine genus is _Phlaeomys_, of large size, and allied to it is _Crateromys_, originally confounded with it. _Batomys granti_ is also confined to Luzon. Its molars are three, like those of the also restricted and Philippine _Carpomys melanurus_, which is an arboreal form.

There is a second species, _C. phaeurus_.

_Phlaeomys_ is placed, however, by Mr. Thomas in a distinct sub-family of its own, PHLAEOMYINAE, and is removed from the Murinae.