524 MR. W. H. FLOWER ON THE OSTEOLOGY OF THE SPERM-WHALE. 
successful whaling-campaign. It will suffice here to point out that, in this part of its 
organization, Physeter conforms with the other Dolphins in the vertically expanded 
hinder part of the ramus, and immensely wide opening of the dental canal (see Pl. LVI. 
fig. 1), characters which separate them from the Whalebone-Whales. It differs from 
the true Delphinide in the excessive length and narrowness of the symphysial portion, 
and consequently great and sudden lateral divergence of the rami posteriorly; but in 
this it resembles the Platanistide, particularly Jnia*. A special peculiarity is, that 
the rami appear never to become united by osseous ankylosis at the symphysis; at least 
this is not the case in the oldest specimen that I have had an opportunity of examining. 
In the largest jaw in the Museum of the College of Surgeons, it was observed, when the 
rami were separated, that the contiguous surfaces were not flat, but that of the left ramus 
somewhat convex in its whole extent, fitting into a corresponding concavity in the right 
ramus. In the jaw belonging to the Tasmanian skeleton, the symphysial portion is 
not perfectly straight, but has a distinct lateral curve, the concavity towards the left. 
This is, however, an individual (though not uncommon) peculiarity. Instances are fre- 
quently met with among Cachalots of excessive curvature of the lower jaw, amounting 
to serious deformity }. 
The gradual increase in the length of the symphysis, compared with that of the 
entire jaw, and the relative decrease in width behind, as age advances, are illustrated by 
the dimensions of three specimens of different sizes in the Museum of the College of 
Surgeons. 
| Mandible of the young skull from ene Eien gabe ee > $8 49" | ay" | 31” 
ETO DOWAGI ase te fierce ele Maier TOM run aoeT Aove Alors, sis casine eae 100 43 ed 63 | 
| Mandible of Tasmanian skeleton ............-....cceecceus 174 | 102 re4 
| IBLOPOLELON pox eid ya: Sedat ME SR EREDatIO ne coe: Oa Re 100 59 “A } 
ieee mandible from Tasmania, presented by Mr. Gutter : i 194 | 124 75 3 
| PEGpOriiOn ese ote eae any Ai wren fhe Sie. ca teeta ae ~~ 400 64 i. 38 
The mandible of the Yorkshire Cachalot is almost identical in dimensions with the 
last of these three. 
The form and structure of the mandibular teeth, their changes with age, and mode 
of implantation are fully described in Owen’s ‘Odontography.’ ‘They present great 
differences both in number and character in different individuals. In the Tasmanian 
* See Description of the skeleton of Inia geoffrensis, Trans. Zool. Soc. vol. vi. p. 89 et seqq. 
+ See Murie, ‘ Proc. Zool. Soc.’ 1865, p. 390. 
t The length is taken from the apex to the middle of a line drawn across the posterior ends of the rami. 
