480 



TE LEO ST EI 



The median fins become outwardly subdivided in a very char- 

 acteristic manner : in the Macruridae there is a small anterior 

 dorsal, as in all Gadiformes, and the long posterior dorsal and anal 

 dwindle gradually to the end of the tapering tail ; but in the 

 Gadidae these two fins become differentiated from a pseudocaudal, 

 and again subdivided into two dorsals and two anals (Fig. 514). 

 The tip of the tail is produced to a fine straight point in Macruridae 



de 



Fig. 510. 



Tail ph. I of the vertebral column of Gadtis morrhua, I.. Only the base of the dermal rays 

 is indicated, c, centrum; </.<-. dorsal (epichordal) dermatrichia ; <l.h. ventral (hypochordal) 

 dermatrichia : '"'■ haemal spine; hy. hypural : no. neural spine : S, detached spine (or radial). 



(gephyrocercal) ; but the homocercal tip is merged, in Gadidae, 

 with portions of the dorsal and anal fins contributing to form a 

 pseudocaudal, having the outward appearance of a diphycercal fin. 

 This tail fin, however, differs considerably in internal structure 

 from that of all other fish ; it has a large dorsal lobe similar to the 

 ventral lobe, and like it supported by the prolongations of a large 

 number of vertebral arches (Figs. 509, 510). 



Division 1. 

 The first vertebra is normally joined to the skull. 



Family Macruridae. Modified deep-sea fish in which the trunk 

 becomes shortened, the tail tapers to a filament, the dentition becomes 



