OCR Text |
Show 1883.] PROF. FLOWER ON THE DELPHINID^E. 477 Such is at present all the material available for the history of these interesting Dolphins. The various individuals described, some from the Cape of Good Hope, some from New Zealand, all present strong points of agreement as to size, form, cranial characters, number of vertebra) and of teeth, and general distribution of surface colouring. They obviously form a natural group; but before we can determine whether to consider them as forming one or more species, we require to know how far the differences hitherto pointed out depend upon errors of observation and imperfect description and delineation, and how far upon individual or sexual variation. It must be noted that hitherto all the Cape specimens recorded have obtusely triangular dorsal fins, while those from New Zealand have had the same organ of a rounded outline. If the two forms should prove to be distinct, the name C. heavisidii, Gray, will be retained for the former, while C. hectori (Van Beneden) will be adopted for the latter, which may or may not include Hector's so-called Electra clancula. If the distinctive characters of the latter should prove to be valid, it will require a new name. A form evidently closely allied, as far as cranial characters tell, is that represented by a skull in the British Museum, from the coast of Chili, to which Dr. Gray gave the name of Delphinus eutropia (P. Z. S. 1849, p. 1), and subsequently erected into the type of his genus Eutropia, under the designation of Eutropia dickiei. Although a second, smaller, and younger skull of the same form has since (in 1881) been received by the Museum from the same locality, nothing is as yet known of its external characteristics, or of the remainder of the skeleton. Specific distinction from C. heavisidii may readily be found in greater size (its extreme length being 360 mm.), longer and narrower rostrum, and larger and rather more numerous (30 to 32) teeth. It must be borne in mind, however, in making this comparison, that all the skulls of C. heavisidii hitherto examined seem to belong to immature specimens, and that the original " Eutropia dickiei " of the British Museum is apparently that of a perfectly adult animal. The form of the pterygoid bones (broken in the type specimen, but preserved in the younger one), however, though of the same general type, is appreciably different from that of those of C. heavisidii. They are longer from before backwards, and their inner edges, though never in contact, are more nearly parallel, and thus approach more nearly to the normal type of the Dolphins. The palate of the larger species also is laterally contracted in front of the pterygoid bones in a manner not seen in the smaller one. Pending the discovery of further evidence as to the characters of this species, I see no reason to separate it generically from Cephalorhynchus, and it should therefore bear the name of C. eutropia. PROC. ZOOL. Soc--1883, No. XXXII. 32 |