THE TELEOSTEI. 



151 



as in the Pike (Figs. 44 & 45), it grows with the growth of 

 the fish, and only becomes partially ossified ; in other cases 

 it almost disappears. A basi-occipital (B.O.), ex-occipital 

 {E.O.], and supra-occipital (S.O.) bone are developed in it. 



AS. MS 



Fig 44. — The cartilaginous cranium of the Pike (Eso.v lucms), with its 

 intrinsic ossifications ; viewed, A. from above ; B, from below ; C, 

 from the left side :— iV, N, nasal fossae ; J.Or, interorbital septum ; 

 a, groove for the median ridge of the parasphenoid ; b, canal for the 

 orbital muscles. Sij., wrongly so marked, is the Pterotic. V. and 

 VIII. mark the exits of the fifth and pneumogastric nerves ; 3, 3, 

 small ossifications of the rostrum. 



and foi-m a complete occipital segment. The proper basi- 

 sphenoid (BS) bone is always a very small, and usually 

 somewhat Y-shaped, bone. The alisphenoids {AS.) some- 



