76 MOMvFISH. 



Sharks and Skates, thus affording an example, in addition to 

 the cartilaginous condition of the bone itself, of apparent 

 conformity with the earlier stage of existence of mammalian 

 animals; and which some writers have thought proper to regard 

 as a defect, or at least an inferior state of development; but 

 wliich, as we have already shewn on the authority of Mr. 

 Owen, when we spoke of the Sharks in general, beyond doubt 

 answers an important use in the natural ceconomy of this 

 great family of animals. We remark it more especially in this 

 species because it is not merely an unclosed opening in the 

 skull, but a well-organized opening of definite formation. It 

 becomes a question whether, by endosmodic action penetrating 

 through the membrane, this is not the passage through which 

 the water so abundantly found in the cavity of the skull and 

 spinal column finds admittance, as we see it existing there in 

 all the species of Sharks and Skates. 



It has been remarked in the general description of this fish, 

 as a character in which it stands alone, that it is deficient in 

 that projection of the skull which is so distinguishing a mark 

 of its kindred families of Sharks and Rays; but the deficiency 

 itself affords an advantage which the others do not possess, of 

 being furnished with such a protractile upper jaw as is capable 

 of extensive motion, especially in an upward direction, cor- 

 responding with that of the head itself, in relationship with 

 the vertebral column. This vertebral column, or back-bone, 

 which possesses about one hundred and twenty separate joints, 

 as in the generality of Sharks, is flexible in all its extent, 

 none of the bones of which it consists being inseparately united 

 together, as they are in the uppermost part of their course 

 in Skates; and at the tail they assume a course seemingly at 

 variance with that of their race in general, by passing to their 

 termination on the border of the lower rather than of the 

 upper lobe of the caudal fin. The organization which seems 

 equivalent to spinous processes of the vertebrae, that stand up 

 to support the dorsal fins, are in fact broad plates, each of 

 which involves at least two of the vertebrae, and thus they 

 afford the fins a more than usually firm support. In these 

 particulars of structure, as well as in the outward form, we 

 discern a partaking of much of the character of the sub-families 

 of Sharks and Skates, coupled with a departure from both in 



