342 PROCEEDINGS OF THE ACADEMY OF 



Var. Ursinii Bp. Pelias chersea vel Ursinii Bp. Fauna Italica. 

 One spec. Italy. Dr. Wilson. 



The gape and muzzle are shorter, and the latter more sloping than usual. 

 In its light colors, our specimen partakes of the character of a young animal. 

 Many specimens of this strongly-marked variety, and much observation on it 

 in a state of nature are needed to settle satisfactorily its true zoological value. 

 Until proof to the contrary can be adduced, we cannot consider it as more 

 than a variety. How far it coincides with the Coluber chersea of Linnseus 

 is a question. 



3. ATRAC TASPIDINjE. 



Bkachychranion Hallowell. 



Proc. Acad. Nat. Sci., vii. p. 99. 



Differs from Atractaspis (Smith, Zool. S. Africa, facing pi. 71) in possessing 

 one pair of frontal plates instead of two. 



In this genus the tympanic bone is short ; but in other respects the me- 

 chanism of the bones of the mouth is similar to that of the vipers and rattle- 

 snakes. The superior maxillary bone is very short and vertical, articulating 

 with the lachrymal by a ginglymoid joint at its superior extremity. Its whole 

 lower surface is occupied by the anchylosed bases of the fangs. The ecto- 

 pterygoid articulates with it moveably, and at a right angle, but is rather 

 short, and incurved posteriorly. While this structure gives its possessor the 

 power of erecting or depressing the fangs, weakness is indicated by the pro- 

 portions and form of the ectopterygoid and tympanic bones, and by the small 

 size of the spheno- and external pterygoid muscles. The former is hot larger 

 than in an adult Tropidonotus sirtalis. Though the gape of the mouth in 

 Dr. Hallowell's species is small, the fangs are probably as efficient as in some 

 species of Elaps, which, it has been shown by the experiments of Dr. Cantor, 

 are unable to inflict a wound on any but very small objects. 



33. B. corpulentum Hallowell. Atractaspis corpulentus Hallow. Proc. 

 Acad. Nat. Sci. 1857, p. 70. Giinther, Cat. Colnbr. Brit. Mus. p. 239. 



One spec. Gaboon. Dr. H. Ford. 



4. CAUSING. . 



Causus Wagler. 



Natur. Syst. Amphib. 172. 



While this genus exhibits a close conformity to the succeeding group in ex- 

 ternal characters, it maintains that modification of the cephalic vertebrae which 

 we deem characteristic of the highest family of Ophidians, the' 'true venomous 

 serpents. 



Thus it is that, while this group (Viperidas) may be distinctly defined by 

 that modification of the ideal by which the neuro-skeletal structure is adapted 

 to an end in the economy of the animal, those external peculiarities which are 

 of no obvious value to their possessors connect it inseparably with that suc- 

 ceeding, and add another to the many proofs that the works of Creation form 

 a graduated and connected whole. 



34. C. rhombeatus Licht. 



One spec. Cape of Good Hope. Garden of Plants. 



Four. Liberia. Dr. Goheen. 



II. NAJID^E. 



1. NAJIN^E. 



Fangs with an external groove, extending from the basal to the terminal 

 orifice. 



Acanthophis Daudin. 



Hist. Rept. v. p. 289, 1803. 



[Dec. 



