UELPHINIDiE. 229 



the sides at nearly equal distances, the hinder ribs closer together at 

 the hinder end. 



Diodouea et Delphina (pars), Rajin. Anal. Nat. 1815, 60. 



Cc'te, Carnivora (pars), Lesson, N. Reg. Anim. 197. 



Hydraula, Ch. Ronaj). Reg. Anim. 



Delpliinusidepe, Lesson, N. Ref/. Anim. 197. 



Delphiniis, Linn.; LUiyer, Prodr. 143, 1811. 



Delphinus et Monodon, Cuv. T<ib. Elem. 1798. 



DelphinidiB (pars), G'/Y/y [Delphinidfe, sect. Delphinina et Plioceniua], 



Ann. Phil. 1828; Sp'ie. Zool. i. 1828; Cat. 3Limm. B. M. 104; Zool. 



Erebus <^ Terror ; Cat. Cetacea B. M. ; Proc. Zool. Soc. 1864, 235 ; 



Ann. S^- Mag. N. H. 1863. 

 Delphinidfe et Monodontidte, Gray, L. Med. Rep. xv. 310, 1821. 

 Cete (pars), Illiger. 



Delphiuidae, Delphinina et Monodoutina, Seh/s-Longchamps, 1842. 

 Les Cetaces piscivores et les Narwals, F. Cuv. D. (S. N. 1829. 

 Zahnwale (pars), Oken, Lehrb. Naturg. 672, 1815. 

 Delphinidse seu Mastrogastera, /. Brookes, Cat. Mas. 39, 1828. 

 Trachyuicliidfe seu Macrodoutea, /. Brookes, Cat. Mus. 40, 1828. 

 Delphiniers, Geoff. Lemons Mammal. 1835, 66. 



This family is easily known from the Toothed Whales or Catodon- 

 tidce by the smaller and- more proportionate head ; and in those 

 species which have lost their upper teeth at an early age, by there 

 being no regular series of pits in the gum of the upper jaw for the 

 reception of the teeth of the lower one ; and also by the upper part 

 of the skull not being deeply concave, and surrounded on the sides 

 and behind by a high ridge. 



These animals when first born are large compared with the size of 

 the parents ; according to Dr. Knox, the foetus of the poi-poise is half 

 the length, that is, one-fourth the size of the parent, before it is born 

 (Trans. Roy. Soc. Edinb. ii. 208) ; and they appear to attain their full 

 size very rapidly, which may account for the very slight difference 

 to be observed in the size of the skull, and the great uniformity in 

 the number, and in the space which the series of teeth occupy upon 

 the edge of the jaws in the different specimens of the same species. 

 Hunter thought the exact number of teeth in any species was un- 

 certain : obser\'ing the teeth in the middle of each series were the 

 largest and the most firmly fixed, he states his belief that "the jaws 

 increase posteriorly and decaj- at the symphysis, and while the growth 

 is going on, there is a constant succession of new teeth, by which 

 means the new-formed teeth are proportioned to the jaw.'' — Phil. 

 Trans. 1788, 898. Dr. Fleming, from the examination of the jaws 

 of two porpoises of different ages, thinks " the jaws lengthen at the 

 symphysis and at the base;" and that "the new teeth formed at 

 these places are the smallest, and that there is no absorption." — 

 Phil. Zool. ii. 208. This may be the case with the specimens before 

 they arrive at their full size ; but no skidl of this kind has fallen 

 under my observation : and as far as my experience will carry me, the 

 numbers, size, and disposition of the teeth furnish the most import- 

 ant characters for the determination of the species and the definition 

 of genera. M. F. Cuvier's remarks (Cetac. 103, 104) on the teeth as 



