172 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



which, however, contrary to those of the opposite side, 

 were placed nearer the posterior edge of the pre-maxilla 

 than the anterior. Dorsally this arm is closely connected 

 with the left pre-maxilla. The posterior arm passes back- 

 wards over the inter-maxillary, with which it is closely 

 connected. At the junction of the two arms a process is 

 sent backwards which is both capped with cartilage and is 

 covered by a further loose moveable piece. This process 

 fits into the excavation on the maxilla already described, 

 and hence the pre-maxilla here overlaps the maxilla. 



Inter-Maxillary Cartilage (I.M.C.). — This cartilage 

 plays an important part in the movement of the jaws. It 

 is asymmetrical, blunt in front but more pointed behind, 

 and forms as it were a pivot on which the two maxillary 

 bones on each side turn. It fits into the depression very 

 obvious in the dried cranium above and to the left of the 

 mesethmoid prominence, and glides up and down from 

 this depression over the prominence itself. Its posterior 

 surface is obliquely grooved, and in such a way that as it 

 moves downwards it passes obliquely over the prominence 

 towards the eyeless side — thus further assisting in the 

 torsion of the jaws to that side. 



Eyeless Side. 

 Articular, Angular and Meckel's Cartilage— The two 



former are slightly larger than the right, and are also 

 slightly more densely calcified, but the differences are 

 small. Meckel's cartilage was in the specimen now 

 described 2mm. longer on this side. 



Dentary. — Appreciably larger and more densely calci- 

 fied, and is strongly curved whilst the right is almost flat. 

 The forking of the posterior margin is further very 

 unequal, the lower limb being much the larger (cp. fig. 5). 

 The depression at about the middle of the outer face of the 



