206 REPTILIA : TESTUDINATA, — XXX. 
aa. Nostrils terminal, crescent-shaped; a prominent longitudinal ridge project- 
ing from each side of septum; head broad ; edge of upper jaw entire. 
ASPIDONECTES, 306. 
305. AMYDA Agassiz. (Lat., turtle.) 
599. A. mutica (Le Sueur), Leatner-Turtie. A depres- 
sion along median line of carapace; no spines nor tubercles along 
anterior margin nor on back. Olive, young spotted ; feet not mot- 
tled below. L. 12. Canada to Ohio R., and N. W. (Lat., un- 
armed.) 
306. ASPIDONECTES Wagler. (dozis, shield; vjxrys, 
swimmer.) 
a. Lower parts of body and feet spotted with dark. 
600. A. spinifer (Le Sueur). Common Sort-sHELLED TourR- 
TLE. Carapace olive brown with dark spots; head and neck olive 
green with light and dark stripes; legs and feet mottled every- 
where with dark; ¢ with the tubercles on the front of the carapace 
smaller than in the 9, the body also longer and the tail extending 
considerably beyond the margin of the carapace. Canada to Ky. 
and Minn., abundant. (Lat., spine-bearing.) 
601. A. nuchalis Agassiz. A marked depression on either side 
of the blunt median keel, which is dilated and triangular anteriorly ; 
spines and tubercles prominent in @. Cumberland and Upper 
Tenn. Rivers. 
aa. Lower parts of body and feet white. . 
602. A. agassizi Baur. Tubercles on shell largest in ¢; back 
blotched in adult; young with black spots and ocelli and with 2 or 
3 concentric black marginal lines. §. Ind. to Ga. and La. 
Famity CXX. CHHELYDRIDAX. (Tue Snaprine 
TURTLES.) 
Shell high in front, low behind ; body heaviest forward ; head and 
neck very large, the snout narrowed forward; jaws strongly hooked, 
and very powerful; tail long, strong, with a crest of horny, com- 
pressed tubercles; plastron small, cross-shaped, with 9 plates be- 
sides the very narrow bridge. Claws 5-4, strong, the web small. 
Large turtles of great strength and voracity, chiefly aquatic; 2 
of the 8 species are American, the third (Platysternum) is from 
China. 
ua. Eyes close together, partly superior; head covered with soft skin; tail with 
two rows of moderate scales beneath; ridges of carapace becoming obsolete 
with age; jaws moderately hooked. «. . . + «. » CHELYDRA, 307. 
aa. Eyes distant, lateral; head very large, covered with smooth, symmetrical 
plates; tail with many small imbricate scales beneath; carapace with 3 
large persistent keels; jaws very strongly hooked. 
MacrocuEtys, 308. 
