948 CLASS PISCES. 



either on the convex or on both borders. It is suggested that they 

 may have been carried on prominences in the caudal region. And 

 after describing the best preserved remains of this genus, Dr New- 

 berry concludes as follows : " Hence, until further light shall be 

 thrown upon the interesting question of the homologies and functions 

 of [the remains of] Edestus, we may regard them as the post-dorsal 

 spines of large cartilaginous fishes, of which the other parts are yet 

 unknown, and may suppose that they w T ere used for attack and de- 

 fence, like the spines of Trygon or Acanthurus." 



Spines of similar type from the Carboniferous of Russia, origin- 

 ally described as Edestus firotofiirata, have been subsequently made 

 the type of the genus Protopirata, although it is doubtful whether 

 this term, having been first made a specific one, is admissible as a 

 general one. 



