SKATES. SS 



proceed from the egg-case, this more slender portion of the body 

 is proportionately of much greater length than in the full-grown 

 animal; but by a process not much unlike that which deprives 

 the tadpole altogether of its tail, the end that lies behind the 

 dorsal fins gradually ceases to receive nourishment, and con- 

 sequ.ently diminishes, so that by the time the fish has attained 

 to about a fourth part of its full dimensions this part is 

 reduced to a much less lengthened condition. In the gener- 

 ality of these fishes there are on this part only two small 

 dorsal fins, but there is more obscurely a slight border of 

 membrane along the sides, and a rudiment that almost resembles 

 a fin which proceeds from the second dorsal to the end. There 

 has also in a very few instances been discovered an elevation 

 of membrane resembling a fin, on the body or disc itself, in 

 one or other of this family; and the circumstance has been 

 deemed of sufficient importance to warrant a belief in the 

 observer that it marked the existence of a distinct species. 

 The first notice of it was by Cuvier, who, however, appears 

 to have doubted whether it was anything beyond an accidental 

 variety of a common species. But Lacepede felt no doubt on 

 the subject, and in his "History of Fishes" he gives a figure 

 and description of it under the name of Cuvier's Ray. It 

 has since been detected in Scotland, and as a mark of a 

 species is adopted by Dr. Fleming, under the same name; but 

 it appears to be at this time the common opinion of naturalists 

 that Cuvier's suspicion was well founded, and that this supposed 

 fin is nothing more than a doubling of the surface of the skin 

 of the back, and is not a sufficient mark that the fish beariner 

 it was a distinct species. It is among what we denominate 

 the aberrant genera of this family that in some cases the true 

 tail exists, in addition to the dorsal fins, and in others no 

 fins of any sort are found. "We shall notice those more 

 particularly when we speak of the different genera. 



So far as is known, and at least among all the members of 

 this family found in the Biilish Islands, all of these fishes 

 produce their young from eggs enclosed in purses; which eggs 

 descend from the ovarian receptacle in pairs, and become 

 excluded in succession, in seasons of the year appropriate to 

 each species. These purses are formed of a leather-like sub- 

 stance, with in general short but rather firm tendrils at the 



