Dr. J. E. Gray on the Species of Ci-ocodiles. 273 



II. Nape with a broad ridge, strongly keeled on each side, and nearly con- 

 tinuous with the dorsal shield, formed of two or three pairs of keeled 

 shields. Legs fringed. Toes webbed. Abnormal Crocodiles. 



* Face broad; nasal bone produced into the nostril. Alligatorian Crocodiles. 



6. Halcrosia. 



The premaxillary suture transverse, rather convex backwards. 

 Nasal bones produced beyond the intermaxillary, and forming a 

 bony septum between the nostrils. The face oblong, broad, 

 without any ridge in front of the orbit. Eyelid with two bony 

 plates. Nuchal plates four, in a cross row, strongly keeled. Cer- 

 vical plates three or four pairs, forming a ridge on each side, 

 the hinder one smaller. Dorsal scales in four series; the central 

 broad, slightly keeled, the outer narrow, distinctly keeled : sides 

 with large convex scales. 



Halcrosia front ata (Black African Crocodile). 



Krokodile noir de Niger, Adanson, MSS., Mus. Paris ; see Cuvier, Oss. 



Foss. iii. 41. 

 Crocodilus palpebrosus, var. 2, Cuvier, Oss. Foss. iii. 41, t. 2. f. 6 (part.). 

 C. trigonatus, part., Cuvier, Oss. Foss. iii. 65. 

 ?C. biscutatus, Cuvier, Oss. Foss. iii. 53, 65 (jun.). 

 ?C. bisulcatus, Bory, Diet. Class. H. N. v. 108 (a misprint?). 

 C.frontatus, A. Murray, Proc. Zool. Soc. 1862. 



Hab. West Africa. Senegal {Adanson); Gaboon ; Old Calabar. 



The Crocodilus biscutatus (Cuvier, Oss. Foss. v. 53, 65, t. 2. 

 f. 6, nuchal plates), from a young specimen labelled "Gavial de 

 Senegal" by Adanson, is probably a young specimen of this 

 species ; but Adanson's name would appear to apply to Mecistops. 



There is a specimen nearly 4 feet long in the Liverpool Mu- 

 seum ; indeed, this seems to be the most common Crocodile of 

 the West- African rivers. 



Cuvier evidently confounded this species with the Alligator 

 palpebrosus of South America ; and it is still confounded with 

 that species by the French naturalists, for we have a skeleton 

 lately sent from the French Museum under that name. 



** Face very long, slender ; nasal not reaching to the nostril. Gavialian 

 Crocodiles. 



7. Mecistops. 



Face subcylindrical, .scarcely dilated in the middle; orbits 

 simple. Nuchal shields numerous, small, in two cross series. 

 Cervical disk narrow, containing two or three pairs of shields. 

 Dorsal shields small, all keeled, in six longitudinal series, lateral 

 one narrowest. Intermaxillary produced behind, and embracing 

 the front end of the nasal. 



This genus has some resemblance to the Gavials ; but the 

 Arm. $ Mag. N. Hist. Ser.3. Vol.x. 19 



