278 Zoological Society, 



united together into one body, and the sixth and seventh are very thin, 

 rudimentary and separate. In Hyperoodon all the cervical vertebrae 

 are rudimentary and united, as in Balarna. In Monoceros the first 

 and second cervical vertebrae are separate and large, and the re- 

 mainder are very thin, separate, and nearly rudimentary. 



M. Cuvier (Oss. Foss. v. 378, 380) has observed that the second 

 and third cervical vertebrae of the Cape Megapteron are united 

 together by their bodies : this does not appear to be the case with 

 the Greenland Megapteron longimanus. 



The union of the vertebrae in the different genera appears to take 

 place at an early period in the life of the animal, for in the skeleton 

 of a young Balasnoptera rostrata which has the epiphysis of the ver- 

 tebrae and arm-bones quite separate, the vertebrae were firmly united. 



Cuvier, in his researches on the Whales (Oss. Foss. v. i. 378, 380. 

 t. 26. f. 13 and 18), observes that the two kinds of true Whale (Ba- 

 Icena) might be distinguished by the form of the lateral processes ; 

 and Professor Eschricht of Copenhagen has made the same observa- 

 tion with respect to the Finner or Pike Whales (Balanoptera) ; and 

 from what I have observed, they appear to present the best character 

 for the distinction of the species, for there can be no doubt that the 

 expanded lateral processes of the Physalus antiquorum must be for 

 a very different purpose, and require very different muscles for their 

 movements than the short lateral processes of Physalus Boops and 

 Sibbaldii. 



In my Essay on the Cetaceous animals published in the ' Zoology 

 of H. M.S. Erebus and Terror,' from the examination of several ske- 

 letons and their fragments and the descriptions of different authors, 

 I attempted to establish that there were three distinct British spe- 

 cies, distinguished by good zoological and osteological characters. 

 Having lately had occasion to examine other specimens, and being 

 enabled to make more minute comparison, I am now satisfied that 

 there is a fourth species which inhabits our coast, and the re-examina- 

 tion of these specimens has enabled me to correct some inaccuracies 

 in my former account. 



In the paper above referred to I proposed to divide the genus Ba- 

 Icenoptera into three subgenera ; but on reconsideration I think it 

 preferable that it should be divided into two genera, retaining the 

 name Balcenoptera for one of the species, and using the old generic 

 name of Physalus for the other three, the genera being established 

 on both zoological and osteological characters. 



Genus Balcenoptera, Piked Whales. 



The pectoral fin one-third and the dorsal fin two-thirds the length 

 of the body from the end of the nose. The second and third cer- 

 vical vertebrae united by the spinous process. The lateral process 

 of the second cervical vertebra rather expanded, united, wing-like. 

 Vertebrae 46 to 48. The pectoral fin moderate, about one-eighth 

 the length of the body. Dorsal fin behind the orifice of generation. 

 Chest with longitudinal folds. 



