| OCR Text |
Show 1883.] PROF. FLOWER ON THE DELPHINID^E. 473 wide open space behind. Between these forms are several intermediate conditions. After the separation of the genera named on p. 468, it is*possible to discriminate among the remainder at least seven distinct types, apparently worthy of generic designation, the characters of which will now be considered. CEPHALORHYNCHUS. Cephalorhynchus, Gray, Cat. Cetacea Brit. Mus. p. 106 (1850). This name may be applied to a group of small-sized Dolphins, which appear to be characterized externally by an obtusely triangular (not falcate) or rounded dorsal fin, small, ovate, or oblong pectoral fins, and rather short rounded snout without groove separating a distinct beak. Both externally and in some of their osteological characters they resemble the members of the genus Phocana. In the skull the rostrum scarcely exceeds half the entire length, is broad at the base, and gradually tapering, with convex lateral Fig. 4. Palate of Cephalorhynchus heavisidii \ borders. The palate is smooth, that is, without the deep, lateral, longitudinal grooves characteristic of the genus Delphinus as now restricted. The pterygoid bones are short aud separated from one another by a considerable interval. The outer edges of the premaxillae form a prominent elevated ridge on each side of the anterior end of the narial aperture. The upper surface of the rostrum itself is very smooth, and evenly rounded from side to side, the surface of the premaxillae in this region being flat and not distinctly elevated above the maxillae. The teeth are small (less than 3 millims. in diameter2), 25 to 30 in number in each side of each jaw. Vertebrae : C. 7, D. 13, L. 15, C. 30 or 31 ; total 65 or 66. The type and best known species of this group is that described by Gray (from a stuffed specimen formerly in the Museum of the College of Surgeons, now in the British Museum), in the ' Spicilegia Zoologica ' (p. 2, 1828) under the name of Delphinus heavisidii. It 1 This figure is from the " Osteographie des Cetaces" of Van Beneden and Gervais, pl. xxvi. fig. 1 A. All the others are from specimens in the Museum of the Royal College of Surgeons. 2 This measurement is in the antero-posterior direction, at the base of the crowns of the largest teeth in the middle of the series. |
