4, OSTEOLEMUS.—5. ALLIGATOR. 289 
stronger on the others. Fingers with a rudiment of web ; outer toes 
hardly half-webbed. Scales on upper surface of limbs keeled; no 
cnemial crest. Adult uniform blackish; young yellowish brown 
above, profusely dotted and spotted with black, and with broad 
black cross bands on the body and tail; ventral shields black and 
yellow. 
Total length 1 metre 70 centim. 
Sierra Leone to Ogowai. 
a. Yg., spir. Old Calabar. A. Murray, Esq. [P.]. 
(Type of C. frontatus.) 
b,c. Ad. & her., skulls, Old Calabar. A. Murray, Esq. [P.]. 
without lower jaws. 
d, Her., stffd. River Bonny. Dy. Forsyth [P.]. 
e. Ad., stffd. W. Africa, 
f,g. Hgr. & yg., spir. W. Africa. 
h. Yg., skel. W. Africa. 
5. ALLIGATOR. 
Alligator, part., Cuvier, Ann. Mus. x. p. 80 (1807); Dum. §& Bibr. 
ili. p. 63 (1836); Strauch, Syn. Crocod. p. 9 (1866), 
Champsa, part., Wagler, Syst. Amph. p. 140 (1830). 
Alligator, Gray, Cat. Tort. $e. p. 66 (1844) ; Huxley, Journ. Linn, 
Soc. iv. p. 3 (1860); Gray, Cat. Sh, Rept. ii. p. 28 (1872). 
17 to 20 upper and 18 to 20 lower teeth on each side; fourth 
maxillary tooth longest ; fourth mandibular tooth fitting into a pit 
in the upper jaw. Snout rather short; nasal bones forming a 
septum dividing the nasal aperture; supratemporal fosse small. 
Splenial bones not entering the mandibular symphysis, which ex- 
tends to the fourth tooth. A dorsal shield formed of six or eight 
longitudinal series of juxtaposed, keeled, bony scutes; gular and 
ventral scutes without or with thin ossifications. 
North America and China. 
Synopsis of the Species. 
The broadest transverse series of dorsal 
scutes composed of 8 scutes; four large 
nuchal scutes; upper eyelid bony an- 
teriorly ; fingers webbed; end of tail 
strongly compressed and crested .... 1. mississippiensis, p. 290. 
The broadest transverse series of dorsal 
scutes composed of 8 scutes ; two large 
nuchal scutes; fingers free ; end of tail 
little serrate above, scarcely compressed 2. helovs, p. 290. 
The broadest transverse series of dorsal 
scutes composed of 6 scutes ; six large 
nuchal scutes; upper eyelid entirely 
bony ; fingers free; end of tail strongly 
compressed and crested ............ 3. stnensis, p. 291, 
