Chap. III. GENERA OF T RIONYCIIID/E. 407 



apace, which project very shghtly in the m.ale Asp. spinifer. The young differ also 

 in having, at birth, comparatively large ocelli upon the carapace, which fade into 

 large blotches in the adult. But the most prominent specific character con.'iists 

 in the marked depressions on either side of the blunt median keel, and also in 

 the triangular dilation of that keel behind the front margin of the carapace. The 

 lower surface of the neck and leet is mottled and speckled, as in Asp. spinifer. 

 Fi-om this scanty information it may be inferred that Asp. nuchalis ranges over 

 the tracks bounded in the south by the distribution of Platypeltis ferox, and in 

 the north by Amyda mutica and Asjjidonectes spinifer. I have received the speci- 

 mens mentioned above too late to cause any of them to be represented upon 

 my plates. 



AspiDONECTES Emoryi, A(/. The first intimation I had of the existence of another 

 species of Aspidonectes within the boundaries of the United States was from the 

 sight of two eggs collected in Texas by Dr. Ileerman, and presented by him to 

 Dr. Ilolbrook, who gave them to me. These eggs (represented in PI. 7, fig. 20) 

 were so much larger than those of either of the three other species of the family 

 which I then kncAV, that I did not he.sitate to consider them as derived from an 

 unknown species. My supposition was very soon changed into certainty, after I 

 had received from the Smithsonian Institution all the specimens of Turtles col- 

 lected in Texas during the operations of the Boundary Survey, under the com- 

 man<l of Col. Emory, among which were young and adult specimens of this spe- 

 cies, collected in the lower Rio Grande of Texas, near Brownsville. I take great 

 pleasure, therefore, in dedicating this species to that distinguished officer. I 

 afterwards received some more young specimens from Mr. G. Stolley, collected in 

 Williamson County,- Texas, in a stream emptjnng into the Rio Brazos. 



This species is very readily distinguished from the two preceding by the ab.sence 

 of prominent spines along the front margin of the carapace, wdiere a single row 

 of small tubercles is visible, and by the greater Avidth of the hind half of the 

 shield, the upper surface of which is dotted all over with small whitish tubercles, 

 like grains of .sand, arranged in longitudinal roAVs along the posterior part of the 

 vertebral column, and diverging somewhat upon the sides, \\\w\\ a uniform greyi.-h 

 ground, without ocelli or blotches. These tubercles are somewhat larger in adult 

 specimens than in tlie young. The pale rim of the hind margin is much Ijroader 

 than in any other species of the family. In young specimens, (PI. 6, fig. 4,) that 

 rim is .separated by a distinct black line, which afterwards fades ; the white tuber- 

 cles are also encircled by faint black line.s, which soon disappear. The whole lower 

 surface is white, except dark lines along the inner surface of the fmgei-s. The 

 upper surface of the legs and the upper part of the neck and of the head are 

 marked with small black dots. A white line extends behind the eyes, and fades 



