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ART. XXIX. — On some New Reptiles from Oregon and the Western Coast of Africa. 



By Edward Hallowell, M. D. 



ONYCHOCEPHALUS. Dumeril and Bibron. 



Generic Characters. — Head provided with plates; depressed, terminating in front 

 in a thin or cutting edge. Rostral plate folded under the snout, and expanding as a 

 disk upon the head, of variable form. An anterior frontal, a frontal properly called, 

 a pair of supra-oculars, a pair of parietals, an inter-parietal, a pair of nasals, a pair of 

 fronto-nasals, a pair of preoculars, a pair of oculars. Nostrils hemidiscoidal opening 

 inferiorly between the nasal and frontal nasal. Eyes lateral, distinct. 



Onychocephalus nigro-lineatus. (Plate xxviii., fig. 1.) 



Specific Characters. — Tail short, of same length as head measured transversely ; 

 rostral plate four-sided, longer than broad, rounded posteriorly, the sides slightly 

 convex; nostrils in the fronto-nasal suture; body cylindrical, slender, presenting 

 numerous lines of black upon a ground of silvery grey. 



Description. — Head small, depressed, convex in front, rostral plate more extended 

 in the longitudinal direction than transversely, its sides slightly convex, rounded 

 posteriorly; the under part of the rostral is urceolate in form, having a small 

 projection at its posterior extremity; it is somewhat excavated laterally, passing 

 backward between the nasal plates ; it presents a well defined edge, at the line of 

 demarcation between its superior portion, extending across it ; the nasals are narrow, 

 oblong plates, placed between the fronto-nasal, and the rostral at its inferior part, in 

 contact above with the fronto-nasal ; the fronto-nasal are situated above between the 

 rostral and the preocular; they are much more narrow superiorly than at their 

 inferior portion, where they are in contact with the nasal ; the nostril, the greater part 

 of which is in the fronto-nasal, occupies the fronto-nasal suture ; the anterior frontal 

 is a well defined plate lying immediately posterior to the rostral, and in contact also 

 in front with the fronto-nasal plates, this portion being excavated to receive the 

 corresponding portion of the latter ; it is convex upon its posterior border, where it is 

 in contact with the posterior frontal and the supraocular, the latter being exterior to 

 it, and also to the fronto-nasal ; the preocular is triangular in form, its widest part 

 being downward, lying in front of the ocular and in contact with the supra-ocular ; 

 the eye, which is small, but distinct, is placed in the angle formed by those two plates ; 

 the ocular is large, convex upon its posterior border : it is in contact above where it 

 forms an acute angle, with the inter-parietal, superiorly with the supra-ocular, 



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