242 A BOOK OF -WHALES 



outwards with the squamosals, as Mr. True has 

 pointed out. This last character is found in Plata- 

 nista ; and it will be borne in mind that the last- 

 mentioned family is characterised among other facts 

 by the freedom of the cervical vertebrae. Delphinap- 

 terus further agrees with Platanista in having a dis- 

 tinct neck. The reduction of the teeth culminating 

 in Monodon is, however, met with in Grampus and 

 Globicepkalus. Finally, a larger number of ribs 

 (eight) than in any others (seven at most), have 

 both capitulum and tuberculum. 



In the following account of the dolphins I shall 

 for the most part admit Mr. True's species (and of 

 course species subsequently described) where there 

 are salient characters. Colour, exact number of teeth, 

 phalanges, and vertebrae are so liable to variation 

 and to wrong enumeration, owing to defective skele- 

 tons, that great care will have to be exercised. 



We will commence with the genus DELPHIN- 

 APTERUS* which has eight to ten teeth of moderate 

 size, occupying anterior part of jaws only. Vertebrae : 

 C. 7 ; D. 1 1 ;t L. 9 ; Ca. 23 = 50. All cervicals free. 

 Eight first ribs two-headed. Four reach the sternum. 

 Pterygoids widely apart, converging towards ex- 

 tremity but not meeting. Phalanges: I, i. II, 6-7. 

 Ill, 4-5. IV, 3-4. V, 3-4 (in embryo 3, 9, 7, 6, 6). 

 No dorsal fin. No hairs on the face. 



* For structure see WATSON and YOUNG in Trans. Roy. Soc. Ed., xxix., 

 p. 393 ; and STRUTHERS, Journ. Ana/. Phys., x., 1896, p. 124. 

 I Occasionally 12. 



