568 



CETACEA. 



nopterae the dentata is anchylosed at its upper 

 part to the third cervical vertebra. In the 

 Cachalots they are the six last vertebrae which 

 are thus found united to one another, and in 

 the Whales, properly so called, or Balance, all 

 the seven are anchylosed. (See Jig. 250.) 



Fig. 250. 



Fig. 252. 



Cervical vertebree of a Whale, Balcena Australii. 



The dorsal vertebrae (I, fig. 246), the number 

 of which varies according to the species, are 

 characterized by having their spinous processes, 

 bent backwards, elongated from the first to the 

 last, and equalled in length by the transverse 

 processes. Moreover, their posterior articu- 

 lating processes disappear after the first ver- 

 tebra, and the anterior ones soon cease to per- 

 form the functions of parts concerned in the 

 union of the vertebrae to one another. 



In Jig. 251, which represents s the eleventh 

 dorsal vertebra of the Cape Whalebone Whale, 

 a is the spinous ; b, b, the two transverse, 

 which begin to lengthen from this point in the 

 succeeding vertebrae; c, c, the anterior articu- 

 lating processes. 



Fig. 251. 



Dorsal vertebra of a Whale. 



The lumbar vertebrae (m, Jig. 246), the 

 posterior limit of which it is difficult to deter- 

 mine in animals devoid of pelvis, have their 

 spinous (a, jig. 252) and transverse processes 

 (b) very long. The first are straight and 

 slightly inclined backwards. 



As it is essential that the Cetaceans should 

 have the posterior part of their vertebral co- 

 lumn left free, to allow of the vigorous in- 

 flexions of the tail required in the act of 



Lumbar vertebra of a Whale. 



swimming, none of the vertebrae are anchy- 

 losed together or encumbered by a union with 

 posterior extremities, and hence there are none 

 which can be properly termed sacral, unless 

 we regard the sacrum as represented by the 

 single vertebra, (n, Jig. 246,) to which, in the 

 Dugong, the pelvic bones are suspended. The 

 caudal vertebrae may then be considered to 

 commence from this point. Most of these 

 vertebrae (o, Jig. 246) are further charac- 

 terized by the chevron bones, (p, Jigs. 246, 

 253,) which at first are strong and well deve- 

 loped, but together with the other processes 

 gradually diminish and disappear towards the 

 extremity of the vertebral column, where the 

 centres or bodies of the vertebrae alone appear, 

 and present a depressed flattened form cor- 

 responding to the horizontal position of the 

 caudal fin, which characterises these air-breath- 

 ing inhabitants of the ocean. 



Fig. 253 represents one of the anterior 

 caudal vertebrae of the Cape W 7 hale : a is the 

 spinous ; b the transverse ; c, r, the represen- 

 tatives of the an- 



Fig. 253. terior oblique pro- 



cesses; p the in- 

 feriorspmous pro- 

 cesses, or chevron 

 bones. 



To bones so lit- 

 tle mobile, and so 

 rudimental as the 

 vertebrae of the 

 neck in Cetace- 

 ans, muscles pro- 

 portionately de- 

 veloped should 

 correspond, and 

 such in fact is 

 the case. The 

 cervical muscles 

 in these animals 

 are the same 

 in number as in 

 other Mammals, 

 Caudal vertebra of a Whale. but their short- 



