riNS OF GANOIBS AND TELEOSTS. 567 



which their rays are supported, the majority of the corresponding 

 rays in Perca. The distal segment of the last radial element 

 supports two rays, and in sutural connexion with the proximal 

 segment of the same element there is a vestigial proximal segment 

 which has no fin-ray. 



All the distal segments in this portion of the fin appear to 

 consist o£ two conjoined lateral halves separated by a distinct 

 median longitudinal suture. 



Anal fin. — There are ten bisegmental radial elements, and 

 behind the last of the series a vestigial proximal segment similar 

 to that in the dorsal fin. The first radial element supports 

 three spines — two by " chain-link " articulations with the distal 

 end of the proximal segment, and the third, the proper ray of 

 this element, by the hooked distal segment. The remaining 

 ten rays are soft and most of them have a " peg-and-socket " 

 articulation with the distal segments o£ their respective radial 

 elements. Tlie distal segment of the last element, however, 

 supports two rays. 



SCOMBEID^. 



Scomber scomber. 



Althougli essentially similar in structure to those of the 

 preceding Acanthopterygian Teleosts, there are nevertheless 

 certain interesting variations in the structure of the dorsal and 

 anal fins in this species. The dorsal fin consists of («) an 

 anterior spinose portion ; (b) a median non-spinose section ; 

 and (c) a series of six detached finlets extending backwards to 

 the root of the caudal fin. It is, however, worthy of note that 

 so far as the supporting radial elements are concerned there is 

 no interruption in the continuity of these externally distinct 

 divisions of the fin. The anal fin also consists of an anterior 

 section succeeded by six detached finlets. 



Anterior Dorsal fin. — Fourteen radial elements are present, 

 all of which are bisegmental. Each of the first nine consists of a 

 proximal segment, with a postero-superior process, and a hooked 

 distal segment. Both the postero-superior processes and the 

 distal segment have well-developed lateral wings, and the medio- 

 dorsal bony groove of which they form the sections is, in conse- 

 quence, unusually deep and broadly Y-shaped. Towards the hinder 

 end of the fin the proximal segments gradually diminish in size, 

 and in the tenth radial element the distal segment loses its 



