324 



BIE. AV. 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 PI. LVI. 

 fig. 1), characters which separate them from the Whalebone-Whales. It differs from 

 the true Delphinidoe 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 Platanistidm, particulai-ly Inia *. 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 f. 



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. 



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. 



t See Murie, ' Proe. Zool. Soc.' 1865, p. 390. 



I The length is taken from the apex to the middle of a line drawn across the posterior ends of the rami. 



