898 THE OSTEOLOGY AND MYOLOGY OF THE DEATH ADDER, 



The postorbital is a semilunar-shaped bone. The upper half 

 of the external surface gives attachment to the subcutaneous tissue 

 which supports the orbital scales ; the lower half becomes twisted 

 on itself so that it comes to be posterior. To this is attached a 

 process of the fascia enveloping the poison gland. The upper half 

 of the internal surface is excavated for articulation with the 

 antero-lateral edge of the parietal ; inferiorly the surface comes 

 to be anteriorly. The superior extremity does not articulate with 

 the frontal as in Pj/thon, while the inferior approaches very 

 near to the transverse bone. This bone forms the posterior portion 

 of the orbital margin, but does not appear to be united to the 

 transverse bone by ligament as it is in Python. Its chief difference 

 from that of the non-venomous snakes is in its superior extremity 

 non-articulating with the frontal. 



Os Nasale. 



Os Nasale, all authors. 



The nasals consist of two bones. Each presents a horizontal 

 and a vertical portion. The horizontal portion is a thin plate of 

 bone triangular in outline. Its superior surface is convex, 

 smooth, and subcutaneous. The inferior surface is concave and 

 forms portion of the roof of the nasal canal. The anterior border 

 is concave and gives attachment to the olfactory capsule. The 

 posterior border also gives attachment to the same capsule. 

 The internal edge is ill-defined being continuous with the vertical 

 plate. The vertical plate is a thin leaf of bone that meets its 

 fellow of the opposite side in the mid-line. They are not anchy- 

 losed together. Posteriorly the septum formed by the two bones 

 runs back to articulate by a pointed extremity with the frontals, 

 while anteriorly they articulate with the premaxilla ; and 

 inferiorly they rest between the angle formed by the olfactory 

 cartilages and the nasal septum. These bones do not differ much 

 in shape from the bones of Python, but in their relations they 

 are quite dissimilar. 



In Python the posterior border articulates throughout its 

 whole length with the prefrontal, while here we see that it has no 



