330 Dr. J. E. Gray on the Species of Alligators, 



even the second cervical scutella have two keels, in others only 

 one ; but this is no specific distinction, as it is not rare to find 

 species with two keels on one side of the neck, and only one on 

 the other. 



2. Caiman. 



Head high, flattened on the sides. Orbits without any ridges. 

 The eyelids smooth, strengthened with a large, single, internal 

 bony plate. The dorsal and ventral scutella bony, articulated 

 together, forming a dorsal and ventral shield; the gular and 

 lateral ventral shields keeled, the abdominal ones smooth ; the 

 cervical scutella four or five pairs, with sometimes one or a pair 

 interposed between the second and third pairs. 



A. Head shelving on the sides. Nuchal scutella Jive, in a single cross series; 

 cervical scutella five pairs j dorsal scutella highly keeled, irregular, in 

 six series J the lumbar scutella in two longitudinal series; the gular 

 and two outer lateral series of ventral scutella keeled. The flat upper 

 disk at base of tail broad and strongly crested. Paleosuchus. 



1. Caiman trigonatus, Gray, Cat. B. Mj 66. 



Crocodilus trigonatus, Schn. Amph. 161, ii. 1. 1,2 (skull); Cuvier, Oss. Foss. 



V. 65. 

 C. palpebrosus, var. 2, Cuvier, Oss. Foss. v. 40, t. 2. f. 1. 

 Champse trigonata, Natterer, Beitr. t. 26 (good). 



Hab. Tropical America. Bt. Domingo (Cuvier). 



Cuvier and Dumeril and Bibron have confounded this species 

 with the Black Crocodile from West Africa ; and we have even 

 received a skeleton of the latter animal from the Paris Museum, 

 under the name of Alligator palpebrosus j var. 



B. Head flat and erect on the sides. Nuchal scutella many, in two cross 

 series ; cervical scutella three pairs ; dorsal scutella slightly keeled ; the 

 lumbar scutella in four longitudinal series ; the gular, the ventral, and 

 lateral abdominal scutella keeled. The flat upper disk at the base of the 

 tail elongate. Aromosuchus. 



2. Caiman palpebrosus. Gray, Cat. B. M. 67. 



Crocodilus sclerops (male), Cuvier, Arch. Zool. ii. 168. 



C. palpebrosus, var., Cuvier, Oss. Foss. v. 38, t. 1. f. 6 & 17, t. 2. f. 2. 

 Champsa palpebrosa, Natterer, Beitr. t. 27 (good). 



Caiman (Jacaretinga) moscifer, Spix, Bras. t. 1. 



Brown ; tail black, banded. 



Hab. Tropical America. 



Natterer figures the head of a species, under the name of C. 

 gibbiceps; but I do not see in what respect it difi'ers from the 

 above, except that the head is a little higher, which is, perhaps, 

 a sexual distinction. 



3. Alligator. 



Head depressed, broad, without any preorbital ridges. The 



