STRUCTURE AND DEVELOPMENT OF LEPIDOSTEUS. 807 



The tail of the eel-like Teleostei is again undoubtedly a 

 modification of the normal form of tail characteristic of the 

 Teleostei, in which, however, the caudal fin has become very 

 much reduced and merged into the prolongations of the anal and 

 dorsal fins. 



This can be very clearly seen in Siluroid forms with an Eel- 

 like tail, such as Cnidoglanis. Although the dorsal and ventral 

 fins appear to be continuous round the end of the tail, and 

 there is superficially no distinct caudal fin, yet an examination 

 of the skeleton of Cnidoglanis shews that the end of the vertebral 

 column is modified in the usual Teleostean fashion, and that the 

 haemal arches of the modified portion of the vertebral column 

 support a small number of fin-rays ; the adjoining ventral fin- 

 rays being supported by independent osseous fin-supports (inter- 

 spinous bones). 



In the case of the Eel (Anguilla anguilla) Huxley (he. cit.} 

 long ago pointed out that the terminal portion of the vertebral 

 column was modified in an analogous fashion to that of other 

 Teleostei, and we have found that the modified haemal arches of 

 this part support a few fin-rays, though a still smaller number 

 than in Cnidoglanis. The fin-rays so supported clearly consti- 

 tute an aborted ventral lobe of the caudal fin. 



Under these circumstances we think that the following state- 

 ment by Mivart (Zool. Trans. Vol. x., p. 471) is somewhat mis- 

 leading : 



"As to the condition of this part (i.e. the ventral lobe of the. 

 tail-fin) in Teleosteans generally, I will not venture as yet to 

 say anything generally, except that it is plain that in such forms 

 as Murcena, the dorsal and ventral parts of the caudal fin arc 

 similar in nature and Jiomotypal zvith ordinary dorsal and anal 

 fins 1 ." 



The italicized portion of this sentence is only true in respect 

 to that part of the fringe of fin surrounding the end of the body, 

 which is not only homotypal with, but actually part of, the 

 dorsal and anal fins. 



Having settled, then, that the tails of Chimaera and of Eel- 

 like Teleostei are simply special modifications of the typical 

 form of tail of the group of Fishes to which they respectively 



1 The italics are ours. 



