CERBERUS BOAEFORMIS. 



OBSERV. There are many more synonymes referred to this species 

 by systematic writers, and which we prefer leaving aside rather than 

 adopt without criticism. 



DESCR. The head is elongated, depressed, subquadrangular or sub- 

 conical, bluntly truncated anteriorly, thickest posteriorly, being slightly 

 swollen upon the temporal region. The cleft of the mouth ascends pos- 

 teriorly, almost at right angles with its horizontal extension, which is 

 nearly straight. The eyes are very small, circular, situated towards 

 the upper surface of the head, and directed obliquely outwards and for- 

 wards ; the pupil is subcircular ; the orbit is composed of five plates : 

 a supraocular, two anteorbitals, and two postorbitals. The supraocu- 

 lars are the largest plates observed on the upper surface of the head; 

 they are longer than broad, and of equal width throughout their length. 

 The superior anteorbital is larger than the inferior one, whilst the in- 

 ferior postorbital is larger than the superior one; both the inferior post- 

 and anteorbitals meet to form the inferior rim of the orbit, thus pre- 

 venting the labials from entering into it. There is a well-developed 

 loral extending obliquely from the fourth labial to the postnasal and 

 the frontals. The latter are four in number: two postfrontals and two 

 prefrontals, the postfrontals being the largest, and nearly equal in size 

 to the loral. A subquadrangular vertex plate, scarcely larger than 

 one of the postfrontals, may be observed posterior to the latter. The 

 nostril is small, situated between two plates on the upper surface of 

 the snout. The prenasal is much larger than the postnasal, and nearly 

 as large as either of the frontals, and situated altogether between the 

 rostral and the prefrontal. 



The rostral is large, pentagonal, and slightly concave upon its base; 

 it is scarcely to be seen in an upper view of the head, its development 

 being altogether vertical, for the snout itself is thick. The upper 

 labials are nine or ten in number, increasing in size posteriorly ; the 

 anterior six, seven, or eight are quite narrow and elevated, whilst the 

 posterior two, three, or four are broader, and disposed upon a double 

 series ; the posterior pair is the smallest of all. The temporal and 

 occipital regions are covered with smooth scale-like shields. There 

 are ten lower labials, increasing in size from the first to the seventh or 

 eighth, and are likewise elevated and narrow ; the eighth, ninth, and 

 tenth are a little larger than the second, third, and fourth. The syru- 

 physeal has the shape of an acute triangle, and is entirely circum- 



