424 Mr. J. Couch un the species of PVhales 



description of Xenacanthus Decheni, Beyrich remarks tliat the 

 teeth resemble those of Diplodus. If evidence were wanting to 

 complete the argument for the approximation of these genera, it 

 is supplied by this fact ; for 1 had the opportunity of determining 

 most conclusively, by the examination of the fine series of spe- 

 cimens exhibited at the meeting of the British Association at 

 Glasgow (1855), that the spines of Pleuracantkus and the teeth 

 of Diplodus belonged to the same fish. 



Through the kindness of Sir Roderick Murchison, I have been 

 enabled within the last few days to settle this matter decisively, 

 by the inspection of a series of most perfect specimens of Xen- 

 acanthus Decheni, Beyr., from the Permian strata of Klein Neun- 

 dorf. The spines of this Permian fish cannot be generically 

 distinguished from those of the genus Pleuracanthus of the Car- 

 boniferous rocks ; neither can the teeth be separated from those 

 of Diplodus of the same age. There are, no doubt, diflferences 

 between them, but these are of specific, not of generic signifi- 

 cance. The genus Orthacanthus of Agassiz has evidently very 

 close affinities with Pleuracanthus ; but the approximation of the 

 lateral rows of tubercles on the under surface of the spine, is a 

 character, perhaps, of generic import. All these spines differ 

 from the defence-bones of the armed Raiidae in having hollow 

 bases. Considering publication as the test of priority, the ge- 

 nera Diplodus (1843) and Xenacanthus (1847) must merge into 

 Pleuracanthus, which was put forth in the ' Poissons Fossiles ' in 

 1837. 



I remain. Gentlemen, 



Your most obedient Servant, 

 P. DE M. Grey Egerton. 



OultonPark, Nov. 17, 1857. 



XLIII. — Remarks on the species of Whales which have been ob- 

 served on the coasts of Cornwall. By Jonathan Couch, Esq., 

 F.L.S. &c.* 



There is no department of Natural History, unless perhaps we 

 except the minute and microscopic, which is so little understood, 

 especially in regard to the distinction of species, as that which 

 comprises the Whale tribe; two or three of which, that have 

 been numbered among British animals, appear to have been con- 

 founded together by different writers, while others have been 

 considered as distinct that are only varieties, and some have pro- 

 bably escaped observation altogether; — circumstances which 

 were the chief inducements to F. Cuvier, brother of the more 



* Abridged from the Report of the Royal Cornwall Polytechnic Society, 

 1856, p. 27. 



