84 ESCHRICHT AND REINHARDT 



ill its posterior part j in the Greenland whale, on the other hand, it grows more in length, so 

 that the upper jaw becomes longer, while the cerebral cavity seems to be removed just as far 

 backwards. With this difference in the direction in which the front wall of the skull principally 

 grows in the Cape whale and in the Greenland whale, the difference existing between them 

 as to the direction of the lateral parts of the ci'anium, must evidently be immediately connected. 



The lateral parts of the cranium consist chiefly of the outwardly directed prolongations 

 {process7is orbitales), of the superior maxillaries and frontals, and the articular portions of the 

 temporals. On either side of the cranium, these three prolongations tend to meet each other, 

 the first two mentioned in a backward, the third in a forward direction, so as almost to meet at 

 their extremities, close behind the orbit. In the Greenland whale, however, some little space is 

 always left between them ; a very strong ligament by which this space is occupied, seems to be 

 the means of attaching them here firmly to one another. The longer these three prolongations 

 grow in an outward direction on either side, the broader the back of the head will, of course, be 

 found to be ; the more they, at the same time, point backwards, the farther backwards its greatest 

 breadth will be, but how far the cavity of the mouth will thus gain in breadth, or in length, 

 depends on whether the glenoid articulations on the lateral portions of the temporals are placed 

 in a more outward, or in a more backward position. 



Now the cranium of the full-grown Greenland whale exceeds in both respects that of all other 

 whales ; the cavity of its mouth being both broader in its posterior part, and more prolonged 

 than that of any other ; as to the breadth of its posterior part, it has already been pointed out by 

 Cuvier, how in the Greenland whale the two glenoid articulations are placed so externally on the 

 lateral portions of the temporals, especially as compared with their position in the Cape whale, 

 that, notwithstanding the less transverse positions of the lateral portions themselves, the glenoid arti- 

 culations are nevertheless much farther removed from each other, and as to the prolongation of the 

 cavity of the mouth, these lateral portions are not only themselves placed rather in a backward, 

 than in an obliquely forward direction, as in the Cape whale, but that the part of them, more 

 especially, on which the articular cavities are placed, is situated so far backwards, that the 

 articulation with the lower jaw in the full-grown Greenland whale is removed even considerably 

 farther backwards than the articulation with the vertebral column.^ 



Thus, while the apparent retrocession of the middle part of the occiput of the Greenland whale 

 is only caused by the immense thickness of the front wall of the cerebral cavity in the longi- 

 tudinal direction of the head, it is, on the other hand, quite certain that a retrocession is to be 

 found in the lateral portions of the temporals, and it is by the position of these very portions, 

 that the great dimensions of the cavity of the mouth posteriorly is effected. The last-mentioned 

 peculiarity only developes itself gradually during growth. In the newborn Greenland whale, 

 the articulation with the lower jaw is still placed a good deal before the occipital foramen 

 {see Plate III, fig. 1, between q and t), in the immature animal it is about on a level with the 

 same.^ The considerable retrocession of the articulation with the lower jaw (in the full-grown 

 Greenland whale, even entirely behind the occipital foramen), can therefore only be employed 

 1 Compare especially figs. 7 and 11 of the often-mentioned plate in Recherch. s. 1. oss. foss. 

 (Ed. 3, torn. V, tab. xxv : in the octavo edition, tab. cxxvi.) 



^ See the figures of the Greenland wfiale cranium in the Museum of Berlin, in Pander and d' Alton, 

 ' die Skelete der Cetaceen,' tab. iv, and in Brandt and Ratzeburg, ' Mediz. Zoo!.,' tab. xvi, figs. 3 

 and 4. 



