NECTURUS MACULATUS. 



421 



Vroc- Cor- 



xSPL 



xxifN/r 



anterior ends, a union which, in a macerated skull, often holds long after the separation of 

 the other components of the jaw. The recurved ventral margin of the dentale becomes 

 closely applied upon the inner side of the mancHble to the corresponding edge of the 

 angulare and usually completes the formation of the intermandibular foramen. The 

 spleniale comes in contact with it by a portion of its outer surface. 



2. ANGULARE. This bone is a curved splint, broad behind and tapering anteriorly 

 into an extremely fine an.l sharp point. Its outer aspect is concaved to receive Meckel's 

 cartilage, and this surface, together with the inner surface of the dentale, forms a nearly 

 complete' canal for the protection of the cartilage just named. The most solid portion of 

 the bone is that which forms its 



lower margin, and this part, when O^Tr. Aspcct 



articulated with the dentale, forms 

 a direct continuation of the flat sub- 

 mental surface of the latter. Poste- 

 riorly it ends in a blunt, rounded, 

 angular process which furnishes at- 

 tachment to the digastric muscle. 

 Along the external aspect of this 

 heavy portion there run a sharp 

 edge for articulation with the ven- 

 tral edge of the dentale, and in this, 

 at about its posterior third, is either 

 a deep notch or a complete fora- 

 men, the former being much the 

 more usual. This is reinforced by 

 the edge of the dentale and forms 

 the mandibular foramen, through 

 which the mylo-hyoid branch of the 

 fifth nerve reaches the intermandib- 

 ular region. The remaining, or dorsal part of the bone forms a flattened and much 

 curved wing ending in a sharp upper edge, the rounding outline of which forms a coro- 

 noid proces°s which receives the insertion of the temporalis muscle. Along the anterior 

 slope of tliis process the upper margin is applied to the lower margin of the spleniale. 



This bone is easily oriented, since the more solid base is ventral and the slight curve 

 of the main axis follows the curve of the jaw. 



3. SPLENIALE. Next to the operculum of the otic capsule, this is the smallest bone 

 of the skull, and by a singular coincidence, many authors have given it the name " oper- 



xSPL 



Ptoc. cor. 



for maw^ifc 



Groove fir 

 MPtkflV cartilage 



Jn N cK Aspect 



Fig. 20. Two views of right, angulare. 

 with other bones are designated by an x. 



X 3. Contact surfaces 



