OCR Text |
Show Side view of cranium of Hyperoodon planifrons. of II. rostratus, as the still unworn (because protected) inner surfaces slope gently outwards and upwards from the edge of the foramen, and the crests therefore, though with a base even broader from side to side than in II. rostratus, must have been low and rounded and quite devoid of any tendency to inversion. Another great difference (better seen in the side view, fig. 2) is that the crests do not sink abruptly at their hinder end, leaving a deeply depressed surface of the maxillary bone intervening between them and the occipital elevation, but they are continued backwards, above the temporal fossa, and so pass gradually into the occipital crests, forming a continuous outer wall to the great basin in which the blowholes are placed, which is completely interrupted in II. rostratus. Among minor differences, 1 Or tbe foramen corresponding to tbe infraorbital in man, in transmitting the brancb of tbe fiftb pair of nerves tbat supplies the cheek and upper lip, but not infraorbital in position in the Cetaceans. |