GREGORY: FISH SKULLS 



309 



Mackerels Tunnies, 5ont/o..-The mackerels and their allies, as is well known are 

 amonTthefa est fish i^ the sea and their locomotor apparatus is excessively specialized, 

 not onlj in he skeleton and musculature, but in the vascular and respiratory system as 

 we r^ such a degree that their body temperature is higher than that of ordinary fishes 

 Tvek th bones reflect the altered physiological properties of the blood-stream as they are 

 Tatu^ated with oil and difficult to degrease. The surface bones are very thin, often smooth. 



nix 



Fig. 187. Rhachycentron. Top view. 



The marked anteroposterior elongation of their opercular -\ P-^P^^^^J^^'^^^^V' Tht 

 ably conditioned also by the voluminous development of the branchial apparatus. They 

 ought to be able to bite hard, for the upper ends of their premaxillaries are coalesced into a 

 sharp, short beak, which lacks distinct ascending processes, is not protrusile and abuts 

 against the massive prevomer and ethmoid. ., j . Aiilc nqd'?^ in a 



' The skull of Scomber scomber (Fig. 188) is --^el/ ^^^^^e^ ^^ f "' ^ f veritable 

 superbly illustrated monograph on the anatomy of this fish. This work is a /eritab « 



reasury of knowledge of structural detail, but for the most part it deals only with Scomber 



