290 CROCODILID A. 
1. Alligator mississippiensis. 
Crocodilus mississippiensis, Daud. Rept. ii. p. 412 (1802). 
— lucius, Cuv. Ann. Mus. x. p. 82 (1807), and Oss. Foss. v. 
pt. ii. p. 82, pls. i. & ii. (1824) ; Tiedem., Opp., § Inb. Nat. Ainph. 
p. 58, pl.iv (1817); Harlan, Med. Zool. Res. p. 146 (1835). 
cuvieri, Leach, Zool. Mise. ii. p. 117, pl. cit. (1815). 
Alligator lucius, Bory de St. Vine. Dict. Class. @H. N. v. p. 100 
(1824) ; Dum. § Bibr. iii. p. 75, pls. xxv. & xxvi. (1836). 
cuvieri, Bory de St. Vine, l.c. p. 104. 
mississippiensis, Gray, Syn. Rept. p. 62 (1831); Holbr. N. Am. 
Herp. ii. p. 53, pl. vi. (1842); Gray, Cat. Tort. §c. p. 66 (1844) ; 
Strauch, Syn. Crocod. pp. 15 & 66 (1866); Gray, Trans. Zool. Soc. 
vi. p. 168 (1869), and Cat. Sh. Rept. ii. p. 29 (1872); Chaffanjon, 
Ann. Soc. Linn. Lyon, xxviii. p. 83 (1882). 
19 or 20 upper and as many lower teeth on each side. Head 
nearly twice as long as broad; snout much depressed, broadly 
rounded at the end, with the lateral outline nearly straight ; a very 
short ridge in front of the orbit; upper eyelid bony anteriorly. 
Two pairs of large nuchal scutes, forming a square, separated on the 
median line, with a pair of small ones in front and another pair 
behind. 17 or 18 transverse series of dorsal scutes, the broadest 
composed of 8 scutes. Fingers hardly half-webbed, outer toes about 
two-thirds webbed. ‘Tail strongly compressed and crested poste- 
riorly. Dark green or blackish above, young with yellowish cross- 
bands; lower parts yellowish. 
Total length 2 metres 20 centim.; reaches a length of 43 metres. 
South-eastern United States, from the mouth of the Rio Grande 
to North Carolina. 
a. Her., stffd. Dauphin Island, Major De Bathe [P.]. 
Mobile Bay. (Type of C. cuvierz). 
b. Yg., spir. New Orleans. 
c-d. Yg., spir. N. America. Lord Ampthill [P.]}. 
e. Ye., stffd. N. America. E. Doubleday, Esq. [ P.]. 
foG,%,%,% Ad., N. America, 
her. & yg., stffd. 
l,m,n,o. Her, & N. America. 
yg., skels. 
p. Ad., skull, N. America. 
g. Ad., skull. N. America. Dr. Falconer [P. ]. 
2, Alligator helois. 
Alligator helois, Cope, Proc. Ac. Philad, 1865, p. 185. 
Two keels behind and between the eyes, diverging posteriorly ; a 
short and nearly transverse keel in frontof the eyes. Two oblique rows 
of elevated horn-like scutes on each side of the neck, of rather small 
size, four in the inner, three in the outer row, the third of the inner 
and the second of the outer forming, with two large elevated median 
scutes, a transverse row. Eight longitudinal rows of dorsal scutes 
