332 AMERICAN TESTUDINATA. Part II. 



as across the sacrum. The ischium is small, the pubis broad and flat ; neither 

 extends downward to any considerable distance from the hip joints. The feet are 

 very large, and longer than that joart of the legs which extends between the knees 

 and elbows, and the joints of the wrist and the ankle. The toes are long, united 

 by a web, and capable of being widely spread ; the inner one is the stoutest, 

 and from thence outward the others are more and more slender, so that the 

 last two, and especially the last one, can serve for little else than to stretch the 

 web ; the middle one is the longest, and on either side of it the others grow 

 shorter ; the first, second, and third, in the genera examined,^ have strong nails, 

 the others none. The inner side of the feet and legs is thick, but from the 

 outer side a broad web reaches out and adds much to the surface presented to 

 the resistance of the water in swimming. The skin is not very closely attached 

 to the legs, and hardly surrounds the front ones at all above the elbows. 



The neck is very long and flexible. The head too is long, and terminated by 

 a long, leathery snout. The brain-box forms a marked angle with the front part 

 of the head, which is distinctly bent downward. The upper surface of the skull, 

 after passing over the brain, turns steejily downward ; the lower surface rises 

 from its hind end to the front end of the brain-box, and fixlls thence forward, 

 but not as steeply as the up23er- surface. The lower jaw grows more flattened 

 toward the front end. The sides of the front part of the head approach each 

 other forward, as in all the other representatives of the order. So the whole 

 fi'ont part of the head, including the lower jaw, tapers to the projecting leathery 

 snout. The mastoids are long, conical, narrow, from the brain-box outward, and 

 taper backward to a point. The opening to the ear cavity is elongated length- 

 wise of the brain-box. The temporal arch is narrow, flat, and thin, and not far 

 removed from the brain-box, so that the passage within it for the temporal muscle 

 is small. The arch, from the top of the skull down to the maxillary, is also 

 narrow, and brought near the brain-box. The j^iirietals project very little or 

 not at all outward. Thus the temporal muscle has a slight, narrow, bony cov- 

 ering. The pterygoids are broad, and have but slight depressions on their outer 

 edges. The sphenoid reaches forward between the pterygoids to the palatines. The 

 openings in the palate, by which the mouth communicates obliquely with the 

 nasal cavity, are large, and extend far back ; the corresponding openings in the 

 back wall of the nasal cavity are also large, and the foramen olfactorium is lai'ge. 

 There is in the skull an opening also in front of the vomer, just within and 

 behind the curved end of the alveolar surface ; but, in life, this opening is filled 

 with a fleshy cushion. 



^ These details are truly family characters, as they determine the form of the feet. 



