17 



the other case, however, in which the terms sphenotic and 

 post-frontal are synonyms, we cannot adopt the same plan, 

 since the term post-frontal cannot be correctly applied to 

 a membrane bone in Fishes. We must hence distinguish 

 between the cartilag-e true sphenotic, or ear bone, and the 

 dermal sphenotic, or lateral line bone, without giving- the 

 latter a definite name. The subject would repay investi- 

 gation. 



Parietal {Par., figs. 1, -3). — Flat conspicuous bones 

 containing of course no cartilage. On the dorsal surface 

 the inner portion is laminate, but the outer portion is 

 much more densely calcified (cp. fig. 1). The boundary 

 separating these two parts is where the skull begins to 

 shelve down. The two parietals are markedly asymmetri- 

 cal, as shown in fig. 1. The parietal is bounded by the 

 supraoccipital, frontal, sphenotic, pterotic and epiotic. 



Alisphenoid [Al.S., figs. 2, 3). — Forms, as described 

 above, a false floor to the cranial cavity, separating the 

 latter from the eye muscle canal. The greater part of the 

 dorsal portion of the alisphenoid consists of two thin 

 plates of bone with a layer of cartilage between them. 

 Behind, the alisphenoid forms the anterior boundary of 

 the foramen for the fifth and seventh cranial nerves, and 

 it is at this region that the bone is most densely calcified. 

 It is bounded by the parasphenoid, prootic, sphenotic, and 

 frontal. In front a portion of the border is free. 



Anterior to the parietal region the asymmetry of the 

 skull is most emphasized, and its rotation in the direction 

 of the hands of a watch is quite manifest. The bones of 

 the two sides therefore differ more or less considerably. 



Right Frontal {R.Fr., figs. 1, 2, 3).— Very elongated 



from before backwards and narrowed from side to side. 



It is the anterior prolongation of the right frontal that 



forms the stout bar between tlie eyes so prominent in the 







