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THE INTELLECTUAL OBSERVER.

APRIL, 1866.

THE MUSK-RATS AS BUILDERS AND MINERS.*

BY J. K. LORD, f.z.s.

(With a Coloured Plate.)

THE genus Fiber has hitherto been based on a solitary species, the well-known musk-rat-Fiber zibethicus of zoologists-the musquash of Canadian trappers and fur traders, the ooklak of the inland Indians west of the Rocky Mountains. Strictly American mammals, musk-rats, true to their native proclivities, are habitual wanderers, regardless of even "Squatter's Preemptive Law," unscrupulously seize on "new locations" that best befit their tastes and requirements.

A summer travelling party of musk-rats, on discovering a desirable spot for a settlement, at once appropriate it. One species sets to work and erects neat little dwellings, that are always placed in the water; the building materials fringe the pool, fixed on as the village site. The other species, diggers by profession, scorn the builder's art, and excavate houses on the bank of some lazy stream or muddy pool.

The requisite establishments complete, the emigrants settle quietly to the "struggle for existence," and patiently bear as best they can, the ills that musquash, like all other flesh, is heir to.

A happy adaptability to extreme climatal changes, enables the musk-rat to endure the scorching heat of an inter-tropical sun, or the nipping cold of an Arctic winter, with trifling

Synoynm.

FIBER ZIBETHICUS, Musk-Rat.

Castor zibethicus, "Lin. Syst. Nat.," i., 1766.
Mus. zibethicus, "Gmelin Syst. Nat.," i., 1788.
Myocastor zibethicus, "Kerr's Linnæus," 1792.
Fiber zibethicus, Cuv., R.A.I., 1817, 192.

Lemmus zibethicus, "Fischer Synop.," 1829, 289.

Ondatra zibethicus, "Waterhouse Mag. Nat. Hist.," iii., 1839, 594.
Musk Beaver, "Pennant's Arct. Zool."

Musquash, Wach-usk of the Cres and Hurms (the animal that sits
on the ice in a round form).

Nov. Sp.-Fiber osoyoosensis (Lord), "Proc. Zool. Soc.," London, 1863.
VOL. IX.-NO. III.

M

inconvenience either to its health or happiness. Throughout the length and breadth of Canada-tenanting the shoals of its countless lakes, the banks of its many rivers, the oozy swamps and muddy, stagnant pools-musk-rats are always to be found. Away into the trackless wastes of the Hudson's Bay Company; by the lone, still ponds scattered over the sunny prairies, or hid neath the shadows of the lofty pines; in dark, miry wastes, amid fungoid growths, sedge plants, and perpetual decay; along the banks of tortuous rivers, from their sources-mere mountain burns, trickling down the craggy sides of the Rocky Mountains-to their mingled exit into the Atlantic, as the great St. Lawrence ;-musk-rats live, thrive, and multiply. Cross the snow-clad heights of the Rocky Mountains, and descend their western slopes, through hotter lands, to the shores of the Pacific; from the Rio-Grande to the desolate regions of Arctic America; through fertile California; grassy, flower-decked Oregon; Washington Territory, with its deserts and mountains; and the densely-timbered wilds of British Columbia, to its junction with Russian America; on rocky Vancouver Island, as well as every island of any size in the Gulf of Georgia ;-musk-rats have found their way, built, and burrowed. It was once supposed, that the musk-rat had made its way to the Asiatic side of Behring's Straits, but there can be but little doubt the skins obtained from Kamschatka and Tschucktchis are traded, or bartered, from native tribes living on the American shores.

There are many structural points of similarity betwixt the musk-rats and Arvicolas, or "field-mice;" still the peculiarly formed feet, flattened tail, much larger size, and singularities of habit in the former, distinctly separates the two genera. Indeed, the musk-rat seems to fill a gap, as it were, between the "field-mice" (Arvicolina) and the porcupines (Hystricida). The sub-family (Casterince), which the famed beaver represents, connects the squirrels and and marmots (Sciurissa), on the one hand, with the gophers (Geomyina) on the other. The teeth of the musk-rat are of arvicoline type. The first and third molars are longer than the second, the second being wider than either of the other two. The grinding surface of the first molar has two indentations or reentrant angles on each side; the second, two outside and one inside; the third, three outside and two inside. The first and third grinders have five prisms or projections on their surfaces, the second four. The loops of enamel extending across the tooth, and joining the enamel that encases the surface, completely isolates the patches of dentine; thus a mill-stone is formed by this most simple contrivance, that improves in grinding power the more it is

worked, and never needs roughing with the stone-cutter's hammer.

In the lower jaw the first molar is much larger than the second and third, which are about equal in length and width. The first having five indentations inside and four outside. The other grinders have each two on either side; the angles are alternate. The upper cutting, or incisor teeth, are broader than the lower, plane in front, but bevelled off at the outside edges, the lower being more rounded away than are the upper. Like the teeth of all the rodents, they are admirably constructed chisels, that by a simple arrangement of hard and softer material, sharpen themselves, the cutting edges becoming keener in proportion to the density of the material gnawed. The muskrat's mouth is truly a marvellous mill, worked by machinery that needs neither steam or water-power to drive it. Its millstones, by the side of which man's best contrivance is but a bunglenever wear smooth, or deteriorate in grinding capabilities, however hard the "miller" works. To supply the mill are admirable nippers that never blunt, and always remain the same length, wear and growth being so admirably balanced.

A very marked peculiarity in the skull of the musk-rat (vide woodcut) is the curious shape of the temporal bone; so compressed is it betwixt the orbits as to narrow the skull into a mere isthmus, not at all wider than the extreme end of the muzzle. Parietals very small; occipital foramen nearly

circular.

Fiber osoyoosensis, Lord, sp. nov. Sp.char.-In total length 3 inches shorter than Fiber zibethicus (Cuv.); in general size much smaller. General hue of back jet-black; but, the hair being of two kinds, if viewed from tail to head, it looks greythe under fur being fine, silky, and light grey in colour; concealing this on the upper surface are long coarse black hairs; the belly and sides somewhat lighter; head broad and depressed; neck indistinct ear small, upper margin_rounded; eye small and black; whiskers long, and composed of about an equal number of white and black hairs; incisors nearly straight, on the external surface orange-yellow.

The thumb of the fore-foot is quite rudimentary; the third claw is considerably longer than the second and fourth. The hind feet are singularly twisted, the inner edges being posterior to the outer. This simple modification of position, gives the animal immense power in swimming. The feet are then bent towards each other; in the backward stroke, the full expanse of the flat soles pushes against the water, sending the swimmer forwards; in the forward stroke the feet are "feathered," like rowers feather an car, passing through the water edge on, offers the least possible resistance. The claws

on the hind feet are small, compressed, and but slightly curved. The skin covering the under surfaces of the feet is black, wrinkled, perfectly naked, and keenly sensitive to tactile impressions. A distinct web joins the digits for about half their length; the upper parts of the feet, are clothed with short lustrous hairs, terminating at the sides in a fringe of stiff bristles, which increase the surface, and give additional force in swimming. Tail nearly as long as the body without the head, cylindrical at the base, then flattened to the point. The tail curves somewhat to a sickle shape; being readily bendable towards the belly, its point can be made to touch the inferior surface of its base; in this position it is almost circular, like a

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Fiber Zibethicus.

Fiber Osoyoosensis.

hoop. This is a highly important arrangement, indispensable to the musk-rat. A more perfect rudder was never designed than is this flexible tail. If swimming when freighted, and a stiff breeze curls the water into miniature waves, the musk-rat drops its tail, and bending it more or less according as it needs extra steering power, guides itself straight for the desired haven. In calm weather and smooth water the rudder is carried horizontally, and a slight lateral motion close to the surface, suffices to guide the living ship. It is worth while to note, en passant, how differently the beaver's rudder is built, as compared with that of the musk-rat's-a difference easily accounted for when we know their respective habits. The

beaver never uses its tail as a trowel, and has no more idea of "lath and plaster" than a hippopotamus has of a polka. This story is a myth, and the sooner the absurd fables of plastering, and "using the wondrous tail as a trowel," are sponged from out all books on natural history the better.

The beaver, with a heavy log of green timber (that would sink like a stone if free) clasped between its fore-legs, swims for its house. The counterpoise to this overweight at the bows is the downward pressure of the flat tail on the water, flattened more horizontally than the musk-rat's. Indeed, the tail of the beaver is much like an ox-tongue in shape. The musk-rat, conveying such materials through the water as are light,

Fiber Zibethicus.

Fiber Osoyoosensis.

needs only powerful rudder-power, having no forward weight to counterbalance. The tail is covered with small hexagonal scales, a few long, coarse hairs irregularly scattered over it. The skull differs from Fiber zibethicus in being much smaller, 2 inches in length, 1 inch in width, very much shorter from the anterior molar to incisors; nasal bones much more rounded at their posterior ends, the superior outline less curved; postorbital process not nearly so much developed; the cranial portion of the skull in its upper outline is much less concave, and smoother; superior outline of occipital bone not so prominent or strong; incisors shorter and much straighter; molars much smaller, but in general outline similar.

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