OCR Text |
Show 1868.] DR. J. E. GRAY ON PTERONURA SANDBACHII. 65 apparent relation to the Sea-Otters, do not exist in the unstuffed specimen from Surinam, which has large feet, with very strong toes united by a broad web extending to the end of the toes, and large acute claws, the feet being quite of the normal or usual form of the Otters', and having no more resemblance to those of the Sea-Otter or Enhydra than is the case in any of the other species of the genus. The skull, which is very long and has sharply tubercular teeth, also shows that it is far removed from the very short, broad, square skull, with the very broad teeth with hemispherical tubercles, that is so peculiar to the Sea-Otter. The Surinam specimen and the reexamination of the Demerara specimen and its skull enable me to give a revised character to the genus:- PTERONURA. Head depressed ; ears hairy, small; muzzle entirely covered with hair. Fur very soft, short, with a fine short soft under-fur. Feet large and strong; toes 5.5, elongate, strong, widely webbed to the ends ; toes on fore feet nearly equal, thumb smaller; the three outer toes of the hind feet are rather longer than the first toes, and the great toe a little smaller; claws large, compressed, acute; soles and palms bald to the heel, striated. Tail conical, tapering, rather depressed, covered with short hair, and furnished with a subcylindrical prominent ridge on each side; end more depressed, two-edged, and fringed at the tip. Teats four, abdominal. Skull elongate, rather high for an Otter ; face very short; nose-opening large, nearly erect; nose with an oblong depression on each side near the orbits; orbits very incomplete, moderate, with a very large oblong aperture beneath the lower edge, and with an obtuse prominence in the front of the upper edge near the side of the nose ; forehead shelving, flat, straight, sides over the orbits straight and short, triangular behind the very small conical supraorbital process; crown with a very narrow central ridge; brain-case very long, twice as long as the face to the back of the orbits, very narrow and compressed in front, broad and swollen behind ; zygomatic arch very strong, broad, leaving a very large wide cavity beneath, infraorbital process slightly marked; the occipital end nearly erect, nearly twice as broad as high ; the foramen magnum oblong, transverse; the upper edge of the foramen thick, concave, with two large roundish perforations close together in the upper part for the passage of two blood-vessels to the brain-cavity. Palate rather concave, narrowed behind, with a square hinder nasal opening. The four central cutting-teeth in each jaw moderate, equal, the outer larger and broader. The premolars conical; the front very small, on the inner side of the hinder edge of the base of the canine ; two others conical, with distinct cingulum. The flesh-tooth large, with the inner lobe nearly as long as the outer edge, oblong, the front side being broadest. The last or tubercular grinder oblong, transverse, nearly twice as broad as long, with four distinct tubercles. The flesh-tooth of the lower jaw oblong, more than twice as long as broad, with three large anterior and one very large posterior lobes; PROC. ZOOL. Soc-1868, No. V. |