Dr. J. E. Gray on a new British Porpoise. 139 



The general form of the head, and examination of the teeth after 

 death, proved at once that it was a species of Phoccena, very nearly 

 allied to, if not identical with, Phoccena communis. 



Dr. Burmeister's description of a Phoccena from the River de la 

 Plata (contained in the Museum at Buenos Ayres), which is peculiar 

 for having some spines on the upper edge of the dorsal fin, naturally 

 made me careful in examining the edge of the fin of this specimen ; 

 and to ray astonishment I discovered that this species also was pro- 

 vided with a series of compressed tubercles, giving the fin a sharp, 

 hard, serrated appearance. 



The tubercles or spines on the dorsal fin having been observed in 

 two specimens from very different localities, I was induced to inquire 

 if this was a character common to the genus, which had been over- 

 looked ; but, on examining the stuffed specimen of the Common 

 English Porpoise in the Museum, it is clear that they are not found 

 in the common state of the species. It then occurred to me that 

 it might be a peculiarity of the male sex ; but Mr. Flower informs 

 me that the male specimen which lived for some weeks in the Gar- 

 dens of the Society, and which he lately dissected, certainly had no 

 spines on the edge of the dorsal fin : so that cannot be the case. 



Under these circumstances I think I am justified in considering 

 that the possession of these spinous tubercles is a peculiarity of the 

 species, and therefore a specific character. The examination of the 

 skull shows that there are differences in its form which confirm 

 this opinion. 



The species of Phoccena may be thus defined : — 



a. Back in front of the dorsal fn, and upper edge of the dorsal fin, 



smooth, without tubercles or spines. Dorsal fin in the middle 

 of the back. 



1. Phocjina communis. 



Hab. North Sea and mouths of rivers. 



b. Back in front of the dorsal fin smooth; the upper edge of the 



dorsal fin with a single series of oblong compressed tubercles, 

 which are more crowded near the upper end of the fin. Dorsal 

 fin in the middle of the back. 



2. Phoccena tuberculifera, sp. nov. 

 Hab. Mouth of the Thames, Margate. 



c. Back in front of the dorsal fin with a single series, and upper 



surface of the dorsal fin with three series, of square-based com- 

 pressed tubercles or spines. Dorsal fin behind the middle of 

 the back. 



3. Phoc.ena spinipinnis, Burmeister, P. Z. S. 1865, p. 228. 

 Hab. Rio de la Plata. 



10* 



