176 DR. J. E. GRAY ON THE TORTOISES. [ Mar. 11, 
logy,’ p. 39, t. 3, it appears to agree with the other American spe- 
cies. If it does, this is another reason why it should not be referred 
to the genus Lutremys, in which Agassiz has placed it in his ‘ Con- 
tributions.’ 
Tribe I. Cistupini1na or North-American Box-Tortoises. 
The temporal muscle only covered with skin. The skull without 
any zygomatic arch between the orbit and the ear-bones. Lobes of 
the sternum moveable at all ages, unequal; front shorter, almost 
free from the symphysis; the hind fixed, narrow, elongate. 
1. Cistupo. 
CISTUDO CLAUSA. 
Skeleton in the British Museum. 
Cistudo clausa, Owen, Cat. Mus. R. C. 8S. p. 192. n. 998 (skele- 
ton), 1009 (skull of young). 
Professor Owen describes a peculiarity in the neural arch of the 
atlas and the other vertebrze, and in the bones of the feet; but he 
does not notice the absence of the zygomatic arch in the skull. 
Fig. 3. 
Cistudo clausa. 
Skull in College-of-Surgeons Museum, No. 999 :—Nose-hole 
square, moderate ; orbit excessively large ; tympanic cavity oblong, 
erect ; upper jaw with a straight lateral edge and a broad central 
part ; palate flat, internal nasal apertures anterior, with a broad tri- 
angular concavity behind them with a central ridge ; alveolar plate 
_ smooth, narrow mm front, rather wider behind ; alveolar surface of the 
lower jaw rather wide, concave. 
