104 BALiENIDjE. 



lower processes of the second and third cervical vertebrae large, thick, 

 short, truncated ; the neural arches very broad and strong, united 

 together, the anterior one forming a large, broad, convex, hood-like 

 body over those of the other cervical vertebrae. 



This genus is established on the cervical vertebrae existing in the 

 Museum at Sydney, New South Wales, of which Mr. Krefft has sent 

 me a photograph, showing the atlas and other cervical vertebrae, seen 

 in front, and the cervical vertebrae without the atlas, seen obliquely. 

 These latter bones seem to me to clearly indicate a species of whale 

 which has not yet been described. On a comparison of them with 

 the figures of the cervical vertebrae of the Bdkena MysticeUis (Cuv. 

 Oss. Foss. V. t. 26. f. 18) and of Eubalcena australis (Cuv. Oss. Poss. v. 

 t. 26. f. 13), they appear to be more nearly aUied to the genus Eu- 

 halcena than to Baleena, but are very distinct from either. These 

 bones differ from both those genera in the atlas being separate and 

 free from the other cervical vertebrae, instead of being all united 

 together into a single mass. In this respect they agree with the 

 cervical vertebrae of the Sperm Whale (Catodon) ; but they cannot 

 belong to that genus, on account of the general form of the vertebra, 

 and especially the form of the neural arch. In both these particvilars 

 they much more nearly resemble the genera Baleena and Eubdkma. 



Genera which have the cervical vertebrae united into one or two 

 masses may be distinguished thus : — 



A. The neural arch of atlas with a strong well-developed ridge on its upper 



edge, forming a keeled crest. 



a. The lateral processes of the atlas on t?ie upper part of the side. Balsenidee. 



* The atlas vertebra united with the other cervical vertebrte into a single hody. 

 Baleena and Eubaleena. 



** The atlas vertebra free from, and separate from, the other cervical ver- 

 tebra. Macleayius. 



b. The lateral process of the atlas and other cervical vertebra on the lower 



part of the mde of the body. Hyperoodon and Lagocetus. Orca 

 crassidens P 



B. The neural arch of atlas low, scarcely raised, keeled on the upper edge ; the 



lateral processes very wide, occupying nearly the whole side-edge of the 

 body of the vertebra. Catodontidae. Catodon. 



The form of the atlas at once distinguishes this genus from Cato- 

 don, or the Sperm Whale. In that genus the atlas is oblong, trans- 

 verse ; the lateral processes occupy the entire side of the body of 

 the bone, and are truncated at the end ; the lower edge is gradually 

 curved from the centre tp the end of the lateral processes ; the upper 

 edge is rather shorter, the middle part over the neural arch being 

 only slightly raised and keeled, and scarcely higher than the upper 

 outer edge of the lateral processes. 



I have named this genus after Mr. MacLeay, the former Secretary 

 of the Linnean Society, and his son William Sharp MacLeay, two 

 naturalists who have done so much for science ; and to the latter 



