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 de- 

 pressed, 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-ease 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. 



