1887.] MR. F. DAY ON A HYBRID CLUPEOID FISH. 1^9 



9. On a supposed Hybrid between the Pilcliard [Clupea 

 pilchardus) and the Herring^ (C. harengus), and on a 

 specimen of Salmo purpuratas. By F. Day, C.I.E. 



[Received February 1, 1887.] 

 (Plate XV.) 



In the mouth of September, 18S6, I received from Mr. Dunn, of 

 Mevagisse)', in Cornwall, a hybrid Pilchard, and in December a 

 second ; also the information that he had seen several, but that the 

 scales had been injured in the remainder. The great interest in these 

 fishes is that, although to a great extent the head most nearly 

 resembles the Pilchard, the scales on the sides of the body show most 

 remarkable differences — in the example which I propose describing 

 consisting of 32 rows along the body and 8 rows in depth on the right 

 side, whereas those along the left side are 51 in number and 10 rows 

 in depth. 



Hybrids among the British Clupeidie have been observed ; thus the 

 Alosa squamopinnata of Couch has been considered by Dr. Giinther 

 to be a cross between the Pilchard and one of the Shads. 



.A cross between a Pilcliard and a Herring would apparently be 

 rather remarkable, as Mr. Dunn found the eggs of the former floating ; 

 however, I was informed by Professor Steindachner that those of the 

 Sardine sink ; and as these are generally accepted as varieties of one 

 species, it still seems doubtful whether the eggs float or sink. While, 

 looking at the form of the head, it may be that the male Pilchard 

 element had been prepotent in both fishes. 



The specimen figured (Plate XV.) has the following characters, and 

 closely agrees with the second example, which is slightly longer, except 

 that the size of the scales is reversed on the two sides of the body, being 

 largest on the left side in the latter. 



D. 17. P. 15. V.8. C.23. L. 1. right side 32 ; 

 left side 51. L. tr. right side 8 ; left side 10. 



inches. 



Entire length S'S 



Length of head I "7 



Length of caudal fin 1'5 



Length of pectoral fin 1 "0 



Height of body 1'7 



Eyes : diameter 0-4 of an inch, 0-5 inch from end of snout, and 

 0-35 inch apart. The head is very similar to that of the Pilchard on 

 the right side, while on the left the raised ridges on the opercles, 

 although very distinct, are not so well marked as upou the opposite 

 side. The form of the body is that of the Pilcliard. Gill-rakers : 

 61 in the lower branch of the outer branchial arch, the longest 

 being 0-35 inch, or not so long as the orbit. In a Herring the 

 number of gill-rakers in the same position was found to be 48, and 



Proc. Zool. Soc— 1887, No. IX. 9 



