168 REPORT OF NATIONAL MUSEUM, 1898. 



than Crocodilns, no undoubted extinct species having been discovered. 

 The neocene Crocodilns spencerU of England has been found to vary in 

 the direction of Alligator, and on such an individual was proposed the 

 A. hantoniensis, but the characters are said not to be normal. 



Species. — Three species of this genus are known. One is the North 

 American; the other is found in China, and the habitat of the other is 

 unknown. Their characters are as follows: 



The broadest series of dorsal scutes composed of eight scutes; four large nuchal 

 scutes; upper eyelid bouy anteriorly; fingers webbed ; end of tail strongly com- 

 pressed and crested A. minsiss'qjjuensis Daudin. 



The broadest transverse series of dorsal scutes composed of eight scutes ; two large 

 nuchal scutes ; fingers free ; end of tail little serrated above, scarcely compressed. 



A. helois Cope. 



The broadest transverse series of dorsal scutes composed of six scutes; six large 

 nuchal scutes; upper eyelid entirely bony ; fingers free; end of tail strongly com- 

 pressed and crested A. sinensis Fauvel. 



ALLIGATOR MISSISSIPPIENSIS Daudin. 



Alligator mississiijpieiisis Gray, Syn. Kept., 1831, p. 62.— Holbhook, N. Am. Herp., 

 II, 1842, p. 53, pi. VI,— GuAV, Cat. Tort., 1844, p. 66.— Stkauch, Syn. Crocod., 

 1866, pp. 15, 66.— Gray, Trans. Zool. Soc, VI, 1869, p. 168; Cat. Sh. Rept., 

 II, 1872, p.29.— Chaffanjon, Ann. Soc. Linn. Lyon, XXVIII, 1882, p. 83. 



Crocodilus mississippiensis Daudin, Rept., II, 1802, p. 412. 



Crocodilns liiciiis CuviER, Ann. Mus., X,1807, p. 32; Ossemeus Fossiles, V, Pt. 2, 

 1824, p. 32, pis. I, II.— TiEDE.MAXN, Oppel, aud Liboschitz, Nat. Amph., 1817, 

 p. 58, pi. IV.— Harlan, Med. Zool. Res., 1835, p. 146. 



Crocodilns ciivieri Leach, Zool. Misc., II, 1815, p. 117, pi. cii. 



Alligator Indus BORY de St. Vincent, Diet. Class, d' H. N., V, 1824, p. 100.— 

 DuMERiL and Bibron, Erp. G6n., Ill, 1836, p. 75, pis. xxv, xxvi. 



Alligator cuvieri BoRY de St. Vincent, Dist. Class, d' H. N., V, 1824, p. 104. 



Nineteen or twenty 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; seven- 

 teen or eighteen transverse series of dorsal scutes, the broadest com- 

 posed of eight scutes ; fingers hardly half webbed, outer toes about two- 

 thirds webbed ; tail strongly compressed and crested posteriorly. Dark 

 green or blackish above, young with yellowish cross bands, lower parts 

 yellowish. 



Total length, 2 meters 20 centimeters; reaches a length of 4^ meters 

 (about 16 feet). 



In young specimens, of a meter in length, the anterior parts of the 

 nasal and maxillary bones present coarse, flat tuberosities, while the 

 middle parts of those bones are nearly smooth. In adults the former 

 regions are nearly smooth, wliile the latter are pitted, producing a 

 shallow honeycombed surface. The posterior parts of the same bones 



