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Show 1887.] MR. F. DAY ON A HYBRID CLUPEOID FISH. 129 9. On a supposed Hybrid between the Pilchard (Clupea pilchardus) and the Herring (C. harengus), and on a specimen of Salmo purpuratus. By F. D A Y , C L E. [Eeceived February 1, 1887.] (Plate XV.) In the month of September, 1886, I received from Mr. Dunn, of Mevagissey, 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 tbe 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 Clupeidae 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 Pilchard 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 8'5 Length of head 1'7 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 rio-ht side, while on the left the raised ridges on the opercles, although very distinct, are not so well marked as upon the opposite side. The form of the body is that of the Pilchard. Gill-rakers : 61 in the lower branch of the outer branchial arch, the longest being 035 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 |
