RODENTIA GEOMYINAE GEOMYS. 369 



edge of the larger and exterior portion of this tubercle is an obliquely inserted fringe of short 

 stiff hairs. The fingers and claws are capable of complete flexure on the palm, the longest 

 claw reaching exactly to this fringe. The claws are all long, curved, compressed, and trenchant 

 below. The claws on the hind feet are much smaller, though thick, stout, and conical. The 

 second is, however, expanded into a spoon shape at the end, a character sometimes 'seen in the 

 first likewise. 



Skeleton. The skull of Geomys is broad and heavy, and considerably depressed ; the muzzle 

 broad above, with the sides throughout nearly parallel, or even wider near the end. Its general 

 shape, in fact, is more or less quadrate, with the broad muzzle projecting in front for from two- 

 fifths to two-sixths the total length. The cranium, with its brain cavity, is small ; and in con 

 sequence of the widely separated zygomata, the orbits are very large, and unusually open when 

 viewed from above. The molars are small ; but the incisors, as well as the entire lower jaw, 

 are enormously thick and massive. 



The nasal bones are elongated, rather narrow anteriorly, and tapering behind to a blunt 

 point. Their backward projection falls considerably short of the posterior extremity of the 

 nasal process of the intermaxillary, which itself reaches to the line of the lachrymals. The 

 nasal process of the intermaxillary is broader midway than the nasal, and makes its appearance 

 on the top of the skull near the end of the muzzle. Its suture with the frontal is difficult to 

 define in the adult, though that with the nasal is always distinct. 



The frontal bones are much reduced in dimensions, owing to the great contraction of the 

 skull between the orbits, the interval here being considerably less than the width of the snout. 

 Their width (the two conjoined, the suture being obliterated at a very early age) is about the 

 same before and behind ; they are much hollowed out laterally, and anteriorly exhibit three 

 processes : one central, passing forward to articulate with the nasal ; the others lateral and 

 pointed, wedging in between the nasal process of the intermaxillary, and the zygomatic of the 

 maxillary, the lachrymal resting against their outer bases. Postero-laterally the frontals are in 

 extended apposition with the very greatly developed squamous portion of the temporal, which, 

 coming up on the superior surface of the skull, covers two-thirds of the whole from the middle 

 of the bony orbit to the occipito-parietal crest. The parietals are thus almost concealed, being 

 excluded from the orbit, and occupying a rather narrow space in the top of the skull, and 

 embraced within the frontals, temporals, and occipitals. 



The occipital bone is quite fully developed, and forms the posterior portion of the skull or 

 occiput, which is truncate and broad, and perpendicular to a horizontal plane. The mastoid 

 portion of the temporal, as in other Saccomyina, is visible in great part postero-laterally. The 

 basilar process of the occipital is rather narrow, and its sides are in close contact with the petrous 

 bone, without any foramen lacerum between. 



Attention has already been called to the unusually great development of the squamous por 

 tion of the temporal bone. This occupies the entire lateral portion of the superior surface of 

 the cranium, the two squamous bones of opposite sides occupying at least two-thirds of the 

 whole. Anteriorly it constitutes the interno-posterior wall of the bony orbit, posteriorly it 

 forms the exterior portion of the occipital crest, and in a notch on the side behind the zygomatic 

 process is seen the tube of the meatus auditorius externus. The glenoid cavity of this bone is 

 long and rather open, its axes converging anteriorly. The outer boundary is constituted 

 entirely by the malar process of the temporal, which extends forwards after bending over the 

 short malar bone. The mastoid and petrous portion of the temporal are in one bone, entirely 

 47 L 



