1S4S.] 59 



Maij 30ih, 1848. 

 Vice President Morton in the Chair. 



(The following papers were reported for publication in the last No. 

 but unavoidably deferred.) 



Description of two new species of Onychncephalus, from the Western Coast of 



Africa. 



By Edward Halloweli., 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 frontonasals, a pair of preoculars, a pair of oculars. Nostrils hemidis- 

 coidal opening inferiorly between the nasal and the frontonasal. Eyes lateral, 

 distinct." 



Onychoeephalus Liberiensis. (See Plate, fig. 1 and 2.) 



Specific Characters. — Length of tail equal to*transverse diameter of head taken 

 at its middle; tail incurvated, conical, terminating in a spin"?; the upper portion 

 of the rostral plate very convex, quadrilateral, its cutting edge slightly arched, not 

 extending across the snout; colour above blackish, variegated with yellow; under 

 surface yellow, with black spots upon the sides. 



De.scripfiun. — Head rather small, wedge shaped above, rounded anteriorly; the 

 rostral plate is large, convex superiorly, presenting four sides at its upper sur- 

 face ; of these the jiosterior is rounded where it lies in contact with the anterior 

 frontal ; the lateral margins are slightly curved and are in contact with the 

 frontonasal; the anterior margin forms a projecting convex edge where it is 

 continuous with the under surface of the rostral which is four-sided; the lateral 

 margins of this under portion of the rostral are concave, so as to receive the nasal 

 plates which lie along their exterior border; the inferior margin is the most nar- 

 row, its mid lie portion, (about one-third of It) projecting backward, and forming 

 part of the margin of the upper lip; the nasal plate is long and narrow, broadest 

 near the middle, being somewhat triangular in shape, the apex presenting forward; 

 the nostrils are elongated narro v slits, looking outward and backward, and are 

 placed in the fronto nasal suture, formed by the juxta position of the nasal and 

 fronto nasal plates ; the fronto-nasal are narrow and o! long, much broader below; 

 anteriorly they lie in contact with the rostral, presenting a slightly undulating 

 line at their junction; the posterior margin is deeply incurvated except toward its 

 superior extremity ; it lies in contact with the preocular which is received 

 into the hollow formed hy its posterior margin; the preocular has the form of an 

 oval disk with a s ip rior and inferior extremity, which are pointed; the ocular 

 plate, which is immediately behind it, is very large; its posterior margin is con- 



