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Show 482 PROF. FLOWER ON THE DELPHINID^E. [Nov. 20, in 1872, not the slightest difference can he detected, either in size or form or in the characters of the teeth. It follows from what has just been said, that of the section (or genus) called Tursiops there are two distinct forms as indicated by tn€* skulls *- 1. T. tursio, including those that have been named metis, eury-nome, cymodice, aduncus, and gillii, some of which may be specifically distinct, but, if so, are very closely allied, and still require definite elucidation of their characters, the principal differences observed in the skulls depending on the comparative breadth of the rostrum, a character much influenced by sex. T. aduncus (T. abusalam, Gray) differs from the rest only in its superior size. . 2. T. catalania, of smaller size than any of the others, and with smaller and more numerous teeth. There is truth in the remark with which Dr. Gray concludes his original description of this species. After comparing it with others of the group, he says :- " It is not easy to point out the distinction of these species in words ; but there cannot be a doubt about them when they are compared together " *. The Dolphins of other groups which present the nearest resemblance to Tursiops, both in external and cranial characters, are those of the section of the genus Clymenia to which C. obscura belongs. STENO. Steno, Grav, Zool. Erebus & Terror, p. 43 (1846). Glyphidelphis, Gervais, Zool. et Pal. Franchises, p. 301 (1859). This group contains also some comparatively large forms of Dolphins, but which differ greatly from the last in the form of the skull. There are no lateral grooves on the palate, and the pterygoid bones are of the normal form, meeting in the middle line (see fig. 6). The rostrum is long, narrow, compressed, and very distinct from the cranium. The symphysis of the mandible is longer than in any of the other Delphinida, exceeding one fourth of the length of the ramus. Teeth 21 to 25 on each side of each jaw, of comparatively large size (5-6 millim. in diameter at base of crown), and in most, if not all the species, with their surfaces roughened by fine irregular longitudinal grooves (which are in a great measure effaced in old individuals) not seen in other Dolphins, and whence the name Glyphidelphis proposed by Gervais for the section. The type of this group is known by skulls only, which are very common in museums, but, as far as I am aware, no skeleton of the species has ever been preserved, and its external characters are most imperfectly, if at all, known. The first published intimation of the existence of the specimens upon which the species was ultimately founded is contained in Cuvier's " Rapport sur diverses Cetace's " &c, in the 'Annales du i P.Z. S. 1862, p. 145. |
