FINS or GANOIDS AND TELEOSTS. 559 



supports gradually diminisli in size from before backwards, and 

 the same may be said of the three sections collectiv^ely. 



Three vestigial radial elements, without distal segments or 

 fin-rays, are interposed between the mesial and porterior dorsal 

 fins. It may in fact be said that, so far as their radial elements 

 are concerned, these fins form a continuous structure, the interval 

 between them which is apparent externally being simply due to 

 the suppression of the three fin-rays corresponding to the three 

 vestigial radial elements. 



No vestigial elements between the anterior and mesial dorsal 

 fins could be detected. 



Anterior anal fin. — This section of the anal fin consists of 

 twenty-five radial elements and twenty-six fin-rays. Of the 

 former, all but the last are bisegmental, and in other respects 

 are very similar to the corresponding structures of the dorsal 

 fin. The last of the series is much smaller than the rest, almost 

 horizontal in position, and, in the absence o£ a distal segment, 

 its cartilaginous extremity supports a feebly developed ray. In 

 addition to its own proper ray, the second of the series, the first 

 radial element supports a feeble ray in front of the former. 



Posterior anal fin. — In this fin there are twenty radial elements 

 and an equal number of fin-rays. All but the last, which lacks a 

 distal segment, are bisegmental. 



As in the case of the mesial and posterior dorsal fins, the 

 interval between the anterior and posterior anal fins is occupied 

 by three vestigial radial elements which complete the continuity 

 of the two series. 



Gadus morrJiua and Merluccius vulgaris. 



In both these Gradoids the radial elements are essentially 

 similar to those of the preceding species. 



Pleuronectid^. 



Pleuronectes platessa. 



Dorsal fin. — The continuous dorsal fin not only extends nearly 

 the whole length of the body but also on to the posterior three- 

 fourths of the head. The supporting radial elements (PI. XXII. 

 fig. 20), including those on the head, are all bisegmental. The 

 proximal segments {p.s.) are long, relatively narrow, vertically 

 disposed structures. Distally, each segment terminates in a 



