380 PHILOSOPHY OF ZOOLOGY. 



(2). Gill openings, one on each side. 



23. CHIMERA. Snout simply conical. C. monstrosa. 



24. CALLORHYNCUS. Snout ending in a fleshy hoe- 

 shaped process. C. antarcticus. 



At the conclusion of this account of the cartilaginous 

 fishes with fixed branchiae, it appears expedient to direct 

 the attention of the reader to the Sea-snake which was cast 

 ashore on Stronsa, one of the islands of Orkney, in Septem- 

 ber 1808. The anatomical characters, furnished by the 

 mutilated fragments which were sent to the Wernerian So- 

 ciety, seem to point out a connection with the genus Squa- 

 lus. But the articulated fins on the sides, the form of the 

 dorsal fin, and the lengthened neck, if the accounts of those 

 who saw the animal can be confided in, prove the pro- 

 priety of the new genus constituted for its reception, and 

 termed Halsydrus, or Sea-snake. Scats. Mag. 1809, p. 7. 

 The structure of the vertebrae of this animal has been 

 explained with great precision by that celebrated anatomist 

 Dr BARCLAY, and figures of some of the parts have been 

 published from the accurate drawings of Mr Syme. These, 

 and the various descriptions of the animal sent from Ork- 

 ney, have been given to the world in the first volume of 

 the Memoirs of the Wernerian Natural History Society 

 of Edinburgh. 



2d Subdivision. 



Branchiae free. This group includes the sturgeons, 

 which have gills like the remaining genera. 



subject, and after having offered a premium for a male thornback with blunt 

 teeth, an intelligent fisherman assured me, he had examined a vast number 

 since I pointed out the distinction of the teeth, and that he could not find 

 one instance of a male with blunt teeth, nor a female with sharp teeth. It 

 may therefore be fairly inferred, that the sexes of the thornback actually dif- 

 fer in this particular, and that the male has probably been described as a 

 different species, but under what title, it is difficult to ascertain, unless it be 

 Raja fullonica of some authors." Mem. Wcrn. Soc. vol. ii. p. 414. 



