40 The Skeleton of the Fish 



noid (14) is a little bone above the myodome or tube in which 

 runs the rectus muscle of the eye. It descends toward the 

 parasphenoid and is attached to the prootic. The prootic (15) 

 is an irregular bone below the ear region and lying in advance 

 of the opisthotic. The alisphenoid (16) is a small bone in the 

 roof of the mouth before the prootic. These sixteen bones 



FIG. 25. Roccus lineatus. Posterior view of cranium. 



6. Parietal. 9. Pterotic. 12. Basioccipital. 



7. Epiotic. 10. Opisthotic. 



8. Supraoccipital. 11. Exoccipital. 



(with a loose bone of specialized form, the otolith, within the 

 ear-cavity) constitute the cranium. All are well developed 

 in the striped bass and in most fishes. In some specialized 

 forms they are much distorted, coossified, or otherwise altered, 

 and their relations to each other may be more or less changed. 

 In the lower forms they are not always fully differentiated, but 



