689 
1908-9.] The Skeleton of a Sowerby’s Whale. 
similar deflection was present in the tip of the mandible. In the Dalgety 
Bay cranium the longitudinal groove was present in the middle third and 
the lateral halves were distinct, the posterior and anterior thirds were not 
grooved, the surface of the medio-rostral bone was smooth and the anterior 
end was pointed. 
In a paper on the development of the rostrum in Mesoplodon, H. O. 
Forbes regarded * the meso-rostral consolidation as an upgrowth formed 
by the proliferation of the osseous tissue of part of the vomer and perhaps 
of the premaxillaries, and not as an ossification of the meso-rostral cartilage. 
The presence of a longitudinal groove, and the consequent indication of 
two lateral halves to the medio-rostral bone, favour to some extent, as 
regards its sides, this view, but I think that ossification of the mesial 
cartilage also participates in the production of the consolidated structure 
which occupies the medio-rostral gutter both in Ziphius and Mesoplodon. 
In the female skull which I described in 1872 the medio-rostral gutter 
did not contain the corresponding bone, which I thought might be a female 
character, but its extensive ossification in the adult female now described 
showed that the absence of the bone in the previous specimen was an age, 
and not a sexual feature. 
The two halves of the St Andrews mandible were not fused at the 
symphysis ; the alveolus for the tooth was situated immediately in front of 
the hinder end of the symphysis, and the apex of the tooth projected for 
only 9 mm. beyond the alveolus ; the retention of the crown within the 
alveolus indicated the female sex. In the mandible of the skull from 
Morrison’s Haven the two halves were in process of fusion, the teeth were 
lost, but the large sockets extended for about half their extent behind the 
symphysis. 
Ear Bones . — In the St Andrews specimen the tympanic bullse and 
petrous bones were lodged in the hollow near the mastoid. The bulla was 
bilobed interiorly and posteriorly, characteristic of the genus Mesoplodon. j* 
Hyoid Apparatus . — The hyoid proper consisted of a body with which 
the two great cornua were fused. At its anterior border was a notch 
bounded by a pair of short processes, each with an articular facet, to 
which the cerato-liyals had doubtless been attached. A well-marked pair 
of stylo-hyals was anterior to and separated by an interval from the 
thyro-hyals. 
Spine , — As the epiphyses were fully anchylosed to their respective 
* Proc. Zool. Soc. Load., 28th Feb. 1893. 
t See my account of the tympano-petrous bones in the Odontoceti, Proc. Roy. Soc. 
Edin., vol. xxiv. p. 423, 1903. 
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