GREGORY: FISH SKULLS 



297 



but the head is shorter and the sagittal crest much higher. Trachypterus (p. 637) retains 

 the marked shortening of the skull, but the occipital crest has disappeared and the bones 

 are very thin and light, almost papery. The skull of Regalecus (Fig. 175), which is de- 



Lampris luna 



Fig. 174. Lampris luna. 



scribed in a beautifully illustrated memoir by T. J. Parker (1886),' is essentially similar 

 to that of Trachypterus, except that it lacks the basisphenoid (Regan, 1907fl, p. 638). The 

 opisthotic is absent, the bone so named by T. J. Parker and by Dunbar (1906) being part 

 of the prootic. In the Veliferidae and. the Trachypteridse there is a large chamber on the 



' See also Befiham and Dunbar, 1906. 



