OCR Text |
Show 250 PROF. HUXLEY ON THE CRANIAL AND [Apr. 6, In this series *±± and -x, as before, increase out of proportion to the rest, and -% undergoes the least alteration; but the upper sectorial increases rather more than the lower, which is the reverse of the relation which obtains in the Alopecoid series. 5. In all young canine animals, the upper edges of the attachments of the temporal muscles are separated by a wide interspace of a lyrate form, with its apex directed posteriorly, which may be called the sagittal area. The boundaries of this area are but little raised; and, as age advances, it becomes gradually diminished by the approximation of the temporal muscles. This approximation takes place Fig. 7. iNat.Size. Upper (A) and lower (B) cheek-teeth of C. lupus, half the natural size ; upper (A') and lower (Br) teeth of C. azarce (a), of the natural size. The first upper molars are thus brought to the same length, and the proportional increase of size of the sectorial teeth of the Wolf is apparent. more rapidly behind than in front, and results in the narrowing, and in most cases coalescence, of the temporal ridges throughout the greater part of the length of the sagittal suture, while in front they diverge to the supraorbital processes and inclose the glabellar area. In the smaller Alopecoids, such as C. zerda, the temporal ridges remain permanently separate, and inclose a wide lyrate sagittal area, the ridges themselves not being very strongly marked ; but in C. littoralis and G. cinereo-argentatus (=C. virginianus) the ridges take the form of strongly-raised cord-like elevations, which impart a very characteristic aspect to the skull (fig. 8, p. 251). In this case there is no sagittal crest. But sometimes there is a well-defined though comparatively narrow sagittal area, from the centre of which a low sagittal crest rises. This is well seen in some Jackals, and especially in C. antarcticus. |