232 MR. H. o. FORBES o^• THE [Feb. 28, 



riorly. In A a line drawn through the meatus audltorius at right 

 angles to the length of the rostrum transects it posteriorly to its 

 crest,'while in older specimens such a line falls anterior to the 

 supraoccipito-frontal suture. Glie crest of the vertex is wider, 

 and the bones which meet there (the nasals, frontals, supraocci- 

 pitals, maxillaries, and premaxillaries) articulate verj loosely with 

 each other. In the youngest form I have examined the nasals lie 

 vertically between the ends of the premaxillaries, the right nasal 

 being on, and the left beneath their level in the vertex ; but as these 

 whales advance in age the nasals sink more deejily between the 

 crest of the premaxillaries, and with the frontals are tightly 

 squeezed together between the premaxillary, maxillary, and supra- 

 occipital bones. The nasal ends of the premaxillaries are less 

 vertical, lower and less everted, and the asymmetry between their 

 right and left portions in the younger individuals is but slightly 

 marked, the right side, however, being always a little larger than the 

 left. The inner borders of the maxillaries are parallel, presenting 

 a gibbosity {cf. fig. 1, (/ih) opposite and extending anteriorly to the 

 maxillary foramina. These gibbosities, which become more marked 

 with age, are but slightly observable in Van Beuedeu's figure and 

 in A, are already more prominent in the Eoyal College of iSurgeons 

 example, and still more so in the intermediate specimens. As I 

 have remarked above, they occur over the intervals in which the 

 vomer does not show on the palatal surface. The premaxillary 

 foramina lie behind those of the maxillary, as usual in this species, 

 and are situated — the right | inch and the left |^ of an inch — 

 anterior to a line joining the anteorbital notches, and also anterior 

 to the forward termination of the ethmoid bone. A line drawn 

 thus in the Kaiapoi specimen (I) runs ol)liquely between the two 

 pairs of foramina, but nearer to the premaxillary foramina than in 

 the type. In the Canterbury Museum example (H) it touches the 

 posterior margins of the right maxillary foramen, and the two 

 pairs are situated nearer than in the type (which closely resembles 

 Flower's haasti in this respect) or in the Kaiapoi specimen, being 

 in the case of the neai'est '25 inch distant (as they are unsym- 

 metrical, the right one of the two is slightly farther apart); in the 

 type they are 1"90 and in the Kaiapoi specimen 1"25 inch apart. 

 In the Royal College of Surgeons example of M. r/nii/i such a line 

 passes midway between the pairs, while in Flower's M. australis it 

 traverses the left premaxillary foramen and comes very near the 

 anterior margin of the right. In the older Otago Museum sjieci- 

 men (F) the right maxillary foramen is j^ inch more posterior to 

 the line than the left, and the pairs are distant, the right 1-^^^ inch 

 and the left 1| inch. It is evident, therefore, that during growth 

 there is a movement of the maxillaries and premaxillaries upon 

 each other, x^hich may not improbably ha^■e something to do with 

 originating the proliferation of osseous tissue in the premaxillaries 

 and vomer. In full-grown specimens these foramina are posterior 

 to such a line and are more nearly opposite the anterior termi- 

 nation of the mesethmoid. The floor and sides of the mesorostral 



