CATALOGUE OF SHIELD REPTILES. 



29 



1. Alligator mississippiensis. (Alligator.) B.M. 



Alligator, Catesby, Carol, t. 63. 

 Crocodilus mississippensis, Baud. Sept. ii. p. 412. 

 Crocodilus luoius, C'uvier, Ann. Mus. x., and Oss. Foss. v. 

 t. 1. f. 8, t. 2. f. 4. 



Tiedem. Amph. p. 58, t. 4. 



Merrem, Zool. p. 34. 



Owen, Cat. Osteol. Spec. Coll. Surg. p. 165. n. 760, 761. 



Blainv. Osteogr. Crocod. t. 2. f. 1, t. 5. f. 1. 



Mil, Skelet. Krokod. t. 8. f. 5, 6, t. 9. f. 3, 1. 10. f. 3, 



4, t. 11. f. 2, 3, t. 20. f. 

 Barm. Gavial. t. 1. f. 3, 4, & t. 3. f. 4. 

 Alligator mississippiensis, Cray, Cat. Tort. $r. B. M. p. 66 ; 

 Ann. tj- Mag. Nat. Hint. x. p. 331 (1862) ; Trans. Zool. 

 Soc. 1869, vi. p. 168. 



Haughton, Ann. .j- Mag. Nat. Hist. (186S) i. p. 282, 

 t. 10 (anat.). 

 Crocodilus Cuvieri, Leach, Zool. Misc. ii. p. 117, t. 102. 

 Alligator lucius, Merrem, Tent. p. 34. 



Bum. 6f Bihr. Erp. Gen. iii. p. 75, t. 25, 26. 

 Alligator Cuvieri, Bory de St.- Vincent, B. C. H. N. v. p. 104. 



Hah. North America, New Orleans, Texas. 



Var. 1. The nose very broad and short. The largest 

 specimen of this variety in the British Museum is nearly 

 4 feet long. 



Var. 2. The nose narrower and longer. The largest 

 specimen in the British Museum is of the same size as the 

 former, which is nearly 4 feet long. Are they the two 

 sexes ? 



The young specimens in spirit have the back black, 

 with narrow white cross bands. The head pale brown, 

 black-varied. Ventral shields in eight or ten longitudinal 

 rather irregular series. 



There is a very young specimen of this species in spirit, 

 from New Orleans, in the Britisli Museum. It is black, 

 with white cross bands. The beak is short, rather slender, 

 with a ridge of skin in front of each eye, giving the appear- 

 ance of a frontal ridge. 



2. Alligator helois. 



" Muzzle 6| inches from end to lines connecting orbits, 

 5f inches wide near the middle. Two keels behind and 

 between the eyes, diverging posteriorly ; a short and nearly 

 transverse keel in front of the eyes. Upper eyelid divided 

 by grooves into three areas ; an elevated keel above each 

 ear-opening. Two oblique rows of elevated horn-like 

 shields 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 second of the outer form, with two large elevated 

 median plates, a transverse row. Four very high, short, 

 keel-like postcervicals. Eight rows of dorsal shields, ex- 



cepting anteriorly, where there are six in the first cross 

 row, and four in the two succeeding : all are like heads of 

 spikes keeled. Four rows on the tail at its middle. Lateral 

 caudal shields continuous, abruptly elevated like the dorsals, 

 subquadrate. Sides with small rounded scales ; width be- 

 tween dorsals and ventrals equal to length of third dorsal 

 cross series. A large row of plates on the inner side of 

 the forearm. Claws long ; no palmar webs. Abdominal 

 rows eleven, each plate with a thin ossification ; two or 

 three large plates in the thoracic cross row. End of tail 

 little serrate above, scarcely compressed. From end of 

 muzzle to occipital 12 inches, to between femora 32 inches ; 

 from latter point to end of tail 50 inches : total 7 feet, 

 10 inches. 



" Colour dark brown, with vertical yellow bars on the 

 sides and tail, the former very irregular. Chin, throat, 

 under and upper lips yellow, without spots." 



Alligator helois, Cope, Proc. Acad. Nat. Sc. Philad. 1865, 

 p. 185. 



" Hah. Unknown (single specimen, Mus. Munich). 



" This rugged-looking species belongs to the genus Alli- 

 gator as restricted by Gray, in which the prolongation of 

 the nasal bones separates the external nares, and there is 

 no cross ridge between the orbits. It approaches Jacan 

 in that an external portion of this cross ridge exists on 

 each side. The habitat is not known, as the single speci- 

 men I have seen preserved is without label in the Museum 

 of the University of Munich. Through the courtesy of 

 Prof. C. von Siebold, I was enabled to make the abovi 

 description." 



Order RHYNCHOCEPHALIA. 



Body with four limbs and elongated tail covered with 

 small scales. Head quadrangular. Belly and underside 

 of tail with four-sided smooth scales, in cross series. Tail 

 with longitudinal ridges of compressed spines. Limbs four. 

 Toes 5-5. Anus transverse. Claspers none. Penis none. 

 " Quadrate bone suturally and immovably united with the 

 skull and pterygoid ; columella present. Parts of the ali- 

 and orbito-sphenoid region fibro-cartilaginous ; rami of 

 mandible united by a short fibrous ligament. Temporal 

 region with two horizontal bars. Vertebras amphiccelian. 

 Copulatory organs none." 



Ithynehocephalia, Giinther, Phil. Trans, clvii. p. 595, t. 26, 



27, 28. 



" Its chief peculiarities consist in the structure of the 



