CHAPTER XII 



CETACEA — WHALES AND DOLPHINS 



Order VI. CETACEA.^ 



Aquatic Maimnalia of fish -like form ; tail expanded into 

 liorizontal Hukes ; a fatty dorsal " tin " present in most species ; 

 anterior limbs converted into fin-like paddles ; posterior limbs 

 only represented by skeletal rudiments. Hairy covering re- 

 duced to a few isolated hairs in the neighbourhood of the 

 nnizzle. Nostrils represented by the single or double blow-hole, 

 nearly always situated far back upon the skull. Bones of loose 

 texture and much impregnated with oil. The skull has a greatly- 

 developed facial portion ; supra-occipital bones meeting the frontal 

 l)y overgrowing, or growing in between the parietals ; bones 

 surrounding the organ of hearing loosely attached to the skull, 

 the tympanies of peculiar cowrie-shell form. Coronoid process of 

 mandible absent, or very feebly developed. Teeth, when present, 

 few or numerous, always of simple conical form, with at most 

 traces of additional cusps (Tnia) ; if absent their place taken by 

 whalebone. Cervical vertebrae of short antero-posterior diameter, 

 often more or less completely welded together into a single mass. 

 Articulations between dorsal and other vertebrae feeble. Scapula 

 peculiarly flattened ; acromion strongly developed as a rule, but 

 arising from a slightly- marked spine ; coracoid process generally 

 strongly developed. Phalanges of digits always more numerous 

 than in other mammals. Clavicles absent. Stomach complex, 

 consisting of at least four and often more chambers. Lungs 

 simple and non-lobulated. Diaphragm obliquely set and very 



^ See van Beneden and Gervais, OsUograpMc des Cetac.es ; and for a more general 

 account Beddard, A Book of Wliales, London, Murray, 1900. 



