44 



FOREST AND STREAM. 



[Atjg. 9, 1888. 



three different kind of mice, to which several new species 

 have been added since this "List" wan published, and 

 three wood rats. Seven true gophers are to be found in 

 our fauna (Geomyidce), seven pouched rats and mice (Sac- 

 comyidce), and a jumping mouse (Zapus). 



Then we have two porcupines, a pika, and finally to 

 complete the list no less than sixteen species of rabbits 

 and hares, and even now, a new species of rodent is be- 

 ing added from time to time to this interesting group. 



Among the United States representatives of this ex- 

 tensive order we have animals of the most widely diverse 

 habits, as for example the rabbits, woodchucks and 

 gophers; arboreal rodents, as the tree squirrels, represented 

 by the gray squirrels; natatorial rodents, as the beaver 

 and muskrat: and we may add aerio-arboreal rodents, as 

 for example the flying squirrels. Our largest rodents are 

 the porcupines and the beaver, and the smallest some of 

 the diminutive and interesting pouched mice. 



Passing to the characteristic structural points as exhib- 

 ited by the Rodentia, we observe among the most striking 

 of these to be certain peculiarities in their teeth. They 

 all lack the canines,while, on either side, the uninterrupted 

 row of molars and premolars may be with or without 

 roots, and their crowns showing either a tuberculated or 

 laminated superior surface. But still more notable are 

 the incisors, for they never exceed two in the lower jaw, 

 and generally a similar number above. These incisor 

 teeth enjoy a continuous growth from persistent pulps, the 

 upper and lower pair worn upon each other, and their 

 cutting edges are kept permanently sharp and ever ready 

 for use: but should the lower pair, for instance, by any 

 means become lost or misdirected, the unopposed upper 

 pair »ontinue to grow on uninterruptedly, curve back- 

 ward into the mouth, the roof which they may even 

 pierce and enter the skull. Many of us have observed 

 such deformed teeth in rabbits, or as I have also seen 

 them in a beaver and a woodchuck. 



As a general thing the collar bones (clavicles) are well 

 developed in these animals, while the plan of their feet 

 may be plantigrade, or somewhat removed from it, with 

 five toes, as a rule, on each foot, and these armed with 

 strong claws, although the latter may be, in some species, 

 but feebly developed. 



In the skull the orbits are not completely surrounded 

 by bone, while in it a number of other characteristic 

 features are to be noticed. Such forms as squirrels and 

 chipmunks possess testes of great size, and through the 

 order these organs may be situated either in the abdomen 

 or thisy may be inguinal. According to Flower, "the 

 uterus is two-horned, the cornua opening separately into 

 the vagina or uniting to form a corpus uteri; the placenta 

 is discoidal and deciduate; and the smooth cerebral hemi- 

 spheres do not extend backward so as to cover any part 

 of the cerebellum." 



In speaking of the teeth I omitted to point out that 

 these animals grow both a "milk" and permanent set, a 

 plan of dentition known as the diphyodont type; and in 

 most rodents the enamel of the incisors is confined to 

 their anterior surfaces, a provision to insure their more 

 certain attrition and sharpening from behind. 



A glance at Fig. 1 will show the semicircular form of 

 one of these incisors, and how, should it continue to 

 grow unopposed by the corresponding tooth of the oppo- 

 site jaw, it would tend to complete the circle, perhaps 

 coming to the roof of the mouth opposite the free end of 

 its own root. All rodents, as we know, are gnawers, and 



Vertical and longitudinal section through the skull of a Beaver 

 (GiWor fiber), showing the cerebral cavity, the greatly devel- 

 oped turbinal laminm, the mode of itnplaitation of the large, 

 tsver-growing, chisel-edged incisor, and the curved rootless 

 molars. Drawn by the author after Flower. 



Side view of the skull of a Beaver (Castor fiber), lower jaw re- 

 moved, showing teeth in the natural skull. Drawn by the 

 author after Huxley. 



Skull of Muskrat (Fiber zibethicus), natural size, showing very 

 large incisor teeth, and the form of lower jaw in a typical 

 Rodent. Drawn by the author after Flower. 



they live for the most part on food that requires the ex- 

 ercise of this mode of obtaining it. Nuts, hard fruits, 

 grain and similar substances hold a high place upon their 

 diet list, while such animals as the prairie marmots eat 

 much grass and some herbs. Mice are almost general 

 feeders, and a year or so ago I pointed out in Science the 

 enormous appetite the "prairie marmots" have for raw 



PLAN OF THE NATIONAL ZOOLOGICAL GARDENS, WASHINGTON. 



meat, a trait common to other rodents, and we are well 

 aware of the muskrat's liking for mussels (Unios), and 

 perhaps other shell-fish. 



Professor Flower well describes another interesting 

 structure of the Rodentia when he writes that "the 

 moutfi is divided into two cavities communicating by a 

 constricted orifice, an interior containing the large in- 

 cisors, and a posterior, in which the molars are placed, 

 the hairy integument of the face being continued inward 

 behind the incisors. This evidently prevents substances 

 not intended for food getting into the mouth, as when 

 the animal is engaged in gnawing through an obstacle. 

 In the hares and pacas the inside of the cheeks is hairy, 

 and in some species, as in the pouched rats and ham- 

 sters, there are large internal cheek pouches lined with 

 the hairy integument, which open near the angles of 

 the mouth and extend backward behind the ears; in the 

 New World pouched rats (Geomyidce) the pouches open 

 externally on the cheeks." 



Last year I owned a wonderfully tame prairie marmot 

 which had been reared by hand from a little thing no 

 longer than my forefinger. It allowed all sorts of liber- 

 ties and pranks to be played upon it without its ever 

 tlnnking of biting one in return, and when picked up by 

 the abdominal integuments, one always noticed three 

 small papilla? protrude themselves from just within the 

 margin of the rectum. These were the opening of a 

 special set of glands which secrete that material which 

 gives rise to the peculiar odor almost constantly notice- 

 able in these animals. Other members of the group 

 have a still more pungent scent about them, emitted 

 from glands of a corresponding nature, but which have 

 in the various species very diverse openings, as into the 

 prepuce in certain mice; or within the exrectal folds as 

 in the jerboas and rabbits; while other species show 

 different apertures for them in the neighboring parts. 



Rodentia exhibit several distinct modes of progression 

 or locomotion, for our Hares and Rabbits, as we know, 

 are great leapers, and progress either by short, or may be, 

 very long leaps; Zapus rapidly gets over the ground by a 

 series of graceful jumps, while the mole- mice tunnel be- 

 neath it quite as expeditiously as the veriest Talpa. 

 Beavers are capital swimmers, while the flying squirrels 

 are possessed of no mean volant powers, rendered possi- 

 ble by the cutaneous expansions which stretch between 

 liinb and limb on either side of their bodies. Finally, 

 among the arboreal Squirrels we find tree- climbers of 

 very pronounced agility and expertness. 



Our rodents, as a rule, are thin-skinned animals, in 

 which the pelage may vary all the way from the soft 

 furry eoat of a hare to the spiny and rough covering of 

 the Canada porcupine; while their tails may exhibit very 

 marked differences, as seen in the beautiful, wavy brush 

 of Abert's squirrel, and the tough, naked paddle of the 

 beaver. 



Both in their skeletons and the rest of their anatomy 

 the several families and even genera present us with 

 much that is interesting, and from a comparative point 

 of view, important; and, although much has been inves- 

 tigated in that direction, there yet remains a vast deal to 

 be examined and carefully described and recorded. Some 

 of our rarer forms have barely had more done for them 

 than the preservation of their hides, by no means the 

 most instructive part of the animal's economy. 



Flower gives the typical dental formula of the order as 

 i\,c %,pm{ or ft, m 1, but I prefer to allude to such points 

 as these when we come to take up the separate represen- 

 tatives of the genera. 



This completes what I have to say in reference to the 

 salient characteristics of the order Rodentia as a whole, 

 and in my next contribution I will take up the animals 

 in the order in which they occur in the U. S. National 

 Museum "List" as given above, commencing with an 

 article on the squirrels or the Family Sciuridce. 



In closing I would add that fossil forms of rodents of 

 great interest have been discovered both in this country 

 and in certain parts of Europe. The most recent of these 

 are closely allied to existing forms, as squirrels, beavers 

 and mice. An extinct beaver has been yielded by the 

 post-pliocene of this country, which in size far exceeds 

 any existing specie's of the Rodentia. and consequently 

 was a great deal larger than the animal of that genus we 

 have with us now (Castorides ohioensis). Many other 

 types have come to light which point to more general- 



ized forms, but it yet remains to discover extinct species 

 which will reveal the line of descent of this order, and 

 define its true ancestry beyond all cavil. 



Zoologists have paid no little attention to the order 

 Rodentia, as a comparatively rich bibliography will 

 attest, and indeed so extensive is the list of works dealing 

 with all that has reference to this, the largest of all our 

 orders of mammals, that it would quite transcend the 

 limitations of space for the present article, even to enu- 

 merate a partial list of them here, so that assistance will 

 of necessity have to be omitted. 



Possibly the opportunity may offer me to give a few of 

 these works in the separate articles on the rodents which 

 I trust to contribute to the columns of Forest and 

 Stream on future occasions. 



NOTES FROM A CANOE. 



Editor Forest and Stream: 



On May 2S, while descending a small Delaware creek in 

 my canoe, an incident happened which struck me at the 

 time as being somewhat out of the ordinary. Being very 

 hot, I had stopped my canoe and was feeling about in the 

 water, when my hand came in contact with some inert 

 substance that I took to be a large water plant bulb. I 

 slowly drew it to the surface, meanwhile pressing and 

 fingering it. As I was about to lift it from the water I 

 was greatly surprised by its suddenly splashing and strug- 

 gling. With a quick movement I threw it into the boat, 

 and then saw that it was an Sin. mullet. On speaking of 

 the matter to a friend he suggested that the fish was 

 asleep. 



On the same trip I was very much impressed by the 

 hiding powers of the chipmunk. A female, chased by a 

 male, stopped on the bank within ten feet of me. The 

 ground was sloping toward me, entirely free from under- 

 brush, and there were but few leaves. I had been look- 

 ing directly at the chipmunk, yet when she stopped she 

 disappeared as completely as if possessed of the legendary 

 magic. The male, who was within four feet of her, 

 began searching everywhere. He was evidently as much 

 at a Joss as to her whereabouts as I was. For about a 

 minute he hunted diligently, often running almost over 

 the spot where I had seen the female last, then he sud- 

 denly detected her and the chase began again. 



The only explanation that I could find was that the chip- 

 munk hid under a leaf, for there was no hole or cavity 

 there to conceal her. J. B. B. 



Hartford, Conn. 



An Ag • d Turtle.— -The papers of July 30 contained 

 this note, dated Lancaster, Pa., July 29: "In 1810 Henry 

 Mogel, a farmer of Centre Township, Berks county, 

 found a land turtle in one of his fields, and cut his name 

 and the year on the under part of its shell. His son, the 

 present treasurer of Berks county, lives on the same 

 farm. A few days ago he was passing through the field 

 and he found the turtle, with the name and date plain 

 on the shell, within a few feet of the spot where the 

 turtle was first found, 78 years ago." We wrote to Mr. 

 Mogel for confirmation of the story, and his reply was as 

 follows: Reading, Pa., Aug. 2, 1888.— Editor Forest and 

 Stream: Yours at hand; in reply I will state that the 

 story about that land turtle is correct, and so is the date. 

 — A. F. Mogel, Dep. Co. Treas. 



Recent Arrivals at Philadelphia Zoological Garden.— 

 Purchased— Two Geoffroy's marmosets (Midas geoffroyi), three 

 gray wolves (Canisoceiden talis griseo-alba), one black bear (Ursus 

 americanus), two yellow-throated parakeets (Brotogerys tovi), 

 one blue linnet (Linaria cannabina), one blue-bonnet parrakeet 

 (Psephotus htematogaster), one blue grosbeak (Goniaphea easru- 

 lea), two large alligators (Alligator niississippiensis), six horned 

 lizards (Phrynosonia cornuta), one royal python (Pytlion regius), 

 five naked-necked iguanas (Iguana delicatissima), two tree boas 

 (Epicrates angulifer) and one pine snake (Pityophis menanoleu- 

 cuo). Presented— Two great horned owls (Bubo virginianus), two 

 wood ducks (Aix sponsa), two common bitterns (Botaurus minor), 

 two American magpies (Pica melanoleuca), one pea hen (Pavo 

 La), two horned lizards (Phrynosonia cornuta), two mud tur- 

 tles (Cinosternum pennsylvanicum), one musk turtle ( Aromoche- 

 lys odoratus), one Muhlenberg's terrapin (Emys muhlenbergii), 

 one copperhead snake (Ancistrodon contortrix), seven painted 

 terrapins (Chrysemys picta), one pine snake (Pityophis menanoleu- 

 cus), two horned rattlesnakes (Crotalus cerastes), and one land 

 tortoise (Cistudo clausa). Born— three beaver (Castor fiber cana- 

 densis), one elk (Cervus canadensis), and one hybrid deer, Caria T 

 cus mexicanus mother, and O. virginianus father. 



