OCR Text |
Show 1883.] PROF. FLOWER ON THE DELPHINID^E. 509 in front of the blowhole. Dorsal fin low and triangular, the length of its base considerably exceeding its vertical height. The type of this genus is G. melas, Traill, of the North Atlantic. Much confusion exists about the other species, or supposed species. I believe that G. melas, like Pseudorca crassidens, has an exceedingly wide range, as the common " Blackfish " of the Australian seas (erroneously called G. macrorhynchus in most catalogues, as that of Hector, Trans. N.-Z. Inst. vol. v. p. 164) appears not to be distinguishable from it either in external or osteological characters. I have examined a considerable series of skeletons both from the Tasmanian and New-Zealand seas, and, comparing them with specimens from the Faroe Islauds, can see no real differences, allowing for the regular change which takes place, especially the increase of the width of the rostrum, with advancing age, and probably also sexual differences not yet understood. Gervais says that the southern skulls have not the rugosities on the upper surface characteristic of old specimens from the north ; but in a skull sent to the College of Surgeons by Dr. Hector from New Zealand these are as well marked as in any that I have seen. There is, however, one form readily distinguished by the shape of the bones of the upper surface of the rostrum. The premaxillae widen out at the middle, so that at this point, and thenceforward to the apex, the maxillaries are completely covered, whereas in G. melas a narrow strip of these bones is seen to form, the lateral part of the rostrum for its whole length. The skull which presents this form, in the Museum of the Royal College of Surgeons, is the type of Gray's G. macrorhynchus (Zool. Erebus and Terror, p. 33, 1846). The teeth are \, aud stouter than in Cr. melas. The specimen was presented by Mr. F. D. Bennett, and is said to be from the South Seas. Skulls of this form exist in many museums, and have been described under different names. One is figured in Van Beneden and Gervais's 'Osteographie des Cetace's,' pl. 52. fig. 3, as G. intermedius, from Guadaloupe; another is Cope's G. brachypterus (Proc. Acad. Nat. Sciences Philadelphia, 1876, p. 129) ; and G. scammoni of the same author, from the coast of California, judging from the photographs sent to the International Fisheries Exhibition, is exactly like the type G. macrorhynchus. I do not mean to imply that there may not be other specific differences between these last, but with only figures of the skulls to judge by, these certainly cannot be distinguished. The type of another of Gray's species, G. affinis, is also in the Museum of the College. The teeth are ~. It is rather narrower than the others, and the premaxillae in the rostrum are more convex laterally, approaching the form of Grampus, in which genus Gray at one time placed it, and from which it is at once distinguished by the presence of teeth in the upper jaw. It is probably only a variety of G. melas. Delphinus intermedius, described by Harlan (Journ. Acad. Nat. Sc. Philadelphia, vi. p. 51, 1829) only from the external characters, is also, in all probability, Globiceps melas. PROC. ZOOL. Soc-1883, No. XXXIV. 34 |