OCR Text |
Show 472 PROF, FLOWER ON THE DELPHINID^E. [NOV. 20, In the same m emoir are also valuable observations upon observed in the number of the vertebrae and ribs, as well as in the external coloration of different individuals, which deserve careful consideration, and as opportunities occur further development and corroboration. Besides the usual distinctive characters derived from tbe length and form of the rostrum and the number and size of the teeth, the condition of the pterygoid bones, though hitherto much neglected, seems to me one of great importance in separating the different Fig. 3. Palate of Belphinapterus tcucas. The pterygoid bones are widely separated in the middle line, and of comparatively simple form, the air-sinus between their lamina? being very little developed. groups of Dolphins. The remarkable involution of this bone, by which it encloses a large air-sinus opening behind between the outer and inner laminae (see fig. 1), is peculiar to the family Delphinida, and is possessed by all its members. Sometimes, in what may be considered the most typical forms (as in Delphinus as now restricted (fig. 9), Tursio (fig. 5), Steno (fig. 6), & c ) , the bones are large, and come into apposition in the middle line by straight surfaces of considerable extent. In others, as Phocana (fig. 2), Monodon, Delphinapterus (fig. 3), they are small and widely separated, having the posterior apex of the palatine bones wedged in between them in front and a |