78 



BAL^NIDiB. 



Yet I think it is so important that we should avail ourselves of 

 eveiy assistance in determining the species of these animals which 

 are so difficult to ohserve, that one must run the risk of making 

 such a mistake, as it can easily he corrected when the opportunity 

 occurs to some competent naturalist to examine a specimen containing 

 hoth the haleen and the ear-bones. 



The tympanic bones are often found fossil. Professor Owen, in 

 the ' Hist. Brit. Fossil Mammals,' has named and figured the ear- 

 bones of the genus Balcena which have been observed in the Crag ; he 

 has named them as if he regarded the following as distinct species : — 

 1. Balaena affinis, flg. 221 ; 2. B. definita, fig. 222 ; 3. B. gibiosa, 

 fig. 223 ; 4. B. emarginata, fig. 224. These bones are aU very im- 

 perfect, and the figures of the two latter are not sufficient even to, 

 decide whether they belong to the genus Balcena or to Physalus. 

 They difier in the recent genera, thus ; — 



Tympanic bone rhombic ; aperture oblong, only slightly contracted 

 at the upper end, and about two-thirds of the length of the 

 bone. Bal-KN A, EuBALaarA, and Hxtntebitts. 



Tympanic bone irregular rhombic ; aperture irregular, much con- 

 tracted at the upper end, and the wide part not half the length 

 of the bone. Capbeea. 



" Dans les galeries d' anatomic comparee du Museum de Paris parmi 

 les preparations des os d'oreiUe nous avons trouve dans un meme 

 cadre une caisse tympanique de Balcena Mysticetus, une autre de 

 Balcena australis, une de Pterohalcena communis, et une de Ptero- 

 balcena gigas." — Van Benedm,in Mem. Acad. Boy. de BruxeTles,l?:&\., 

 xxxii. 38. 



Synopsis op the G-eneea. 



I. Atlas united loith the other cervical vertebra into one mass ; the lateral 

 process of the axis small, broad, solid. 



A. Baleen thin, polished, with a thick enamel coat and a ^ne fringe. 



1. Bal^na. First rib slender near, and undivided at the vertebral end. 



Tympanic bone square ; aperture nearly as long as the bone. 



B. Baleen thick, not polished, with a thin enamel coat and a coarse thick 



fringe. 



2. Eubai^na. First rib broad at the vertebral end. Tympanic bone 



square ; aperture nearly as long as the bone. 



3. HuNTEBius. First rib broad, with a double head at the vertebral end. 



Tympanic bone square ; aperture nearly as long as the bone. 



4. Capebba. First rib ? Baleen ? Tympanic bone irregular 



rhombic ; aperture in-egular, much contracted at the upper end, and 

 the wide part not half the length of the bone. . 



n. Atlas free from the other cervical vertebra, which are united into a 

 single mass ; the lateral process of the axis rounded. 



5. Macleayius. The lateral process of the axis truncated. 



6. ? PALiEOCETTTS. The lateral process of the axis produced, rounded, 



slightly perforated. 



