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TRANSACTIONS OF THE AMERICAN PHILOSOPHICAL SOCIETY 



anterior part of the cranium, the walls formed by the frontals, the floor partly by the 

 mesethmoid (Regan, 1929). This chamber is absent in the other families of the order. 

 Thanks to the kindness of Dr. Tate Regan and Mr. J. R. Norman of the British 

 Museum (Natural History), I have had the privilege of studying excellently prepared skulls 

 of Velifer hypselopterus (No. 527.^, Brit. Mus. Nat. Hist. (Fig. 173)) and of Lampris Inna 

 (Fig. 174). The former appears to me to be much nearer than the latter to the origin of 

 the group. Apparently the peculiar character of the maxillae, noted by Tate Regan, permit 

 nearly the entire protrusile portion of the upper jaw, including the articular processes of 

 the maxillas, to slide on the vomer and thus to be retracted into the chamber that lies 

 above the mesethmoid and below the dorsal flanges of the frontal. In Lampris this ar- 

 rangement appears to be in a degenerate condition and the median cavity between the 



na 



pa ptm htjin 



pm)( 



Regalecus argenteus 



Regalecus glesne 



Fig. 175. Regalecus argenteus. After T. J. Parker. 



frontal flanges has disappeared. It need hardly be said that the latero-dorsal surfaces of the 

 frontal flanges serve as a base for forwardly-produced muscles of the nuchal crest. 



Velifer also seems to be more primitive than Lampris in the entire opercular region. 

 In the line leading to Lampris, apparently in correlation with the change in body form 

 from very elongate to orbicular, the horizontal diameter of the fore part of the skull has 

 been shortened in relation to its vertical diameter, that is, the mandible has become much 



