SPOTTED- DOLPHIX. 



321 



Measurements of Ihe skull of Ptodelphinitu doris, Xo. ^^^5^?, i ; the fijpe of P. i)Ia<ji<Hh»i, 

 No. 3884 ; and the type of P. doris, British Museum, Xo. 352a. 



Measurements. 



I P. doria. Xo. 



i 21915, U. S. 



Kat. Mas. 



Typoof P.pto- 

 giodon, Xo. 

 3p«4. U. S. 

 Xat. Mas. 



Type of P. 

 do rig, Xi). 

 352a. Brit. 

 Mu&. 



cm. ' lOOths. cm. 



lOOths. 



cm. lOOths. 



Total length 46.2 



LeD'.'lli of beak 26.9 



Breatltb of beak at ba.se of notches 10. 1 



Bieaillli of beak at its middle 5.8 



Breadth of intennaxillaries at same point ' 3. 3 



firtate-it bri-iidth between outer margins of inter- 



maxillaries. proxtmally ' 8. 1 



Len-ith of tooth-lino 23.6 



Last toith to base of maxillary notch 5. 3 



Tip of beak to anterior niar<;in superiornasal open 



in>: 32.4 



Tip (if b« ak to end of crest of pteryjroid 34. 7 



Breadth between orbital ))iopesses of frontal 18.5 



Ibeadih betwei a hinder niar^jins of tcuipural fosssB.i 14.4 



I.enLTtb of temporal fossa 8. 1 



Depi h of temporal iVwsa 5. 6 



Total length of inaudible 39. 2 



Depth between anfjle and coronoid process ] 7. 3 



Ileifrlit of crown of lariiest tooth .8 



Greatest diameter .if crown at base ' .5 



Number of teeth i ?I=p 



33-34 



100.0 



58.2 



21.9 



12.6 



7.1 



17.6 

 51.1 

 11.5 



70.3 

 75. 2 

 40.1 

 31.3 

 17.6 

 12.1 

 85.2 

 15.9 



43.1 



24.3 



9.1 



5.6 



2.8 



7.8 



21.0 



4.6 



28.0 



100.0 



56.5 



21.2 



12.9 



6.5 



18.2 

 48.2 

 10.6 



6.5.9 



18.0 

 14.2 

 8.1 

 6.1 

 36.7 

 7.1 



35-35 

 34-35 



41.8 

 32.9 

 18.8 

 14.1 

 85.2 

 16.5 



39 2 I 

 2.3.4 



9.4 i 



4.9 



2.7 I 



7.3 j 

 20.2 



4.0 I 



26.9 ' 

 28.7 

 16.3 

 13.1 ( 



7.1 I 

 5.3 I 



33.8 

 CO 



38-34 

 34-34 



100.0 



:>% 9 

 2:i. 9 



11.9 

 7.1 



13.8 

 51.8 

 10.4 



68.6 

 73.1 

 41.7 

 33.3 

 18.1 

 13.6 

 86.4 

 15.5 



TAXONOMY, 



The majority of specie.s of Del ph in idee Are founded upon single skulls. 

 All dolphins' skulls differ from one another to a greater or less extent, 

 and it is impossible, therefore, to find any which will agree exactly with 

 the types. Furthermore, the limits of cranial variation have been deter- 

 mined only in the case of two or three well-known sjiecies. For these 

 reasons there is a strong temptation, when a fresh s])ecimen of which 

 the external characters are undescribed is acquired, to erect a new spe- 

 cies. The skull presents differences which separate it from the type 

 skulls of any ])reviously described species, and there is no criterion by 

 which one may judge whether these differences are of si)eciflc value or 

 onl}^ represent individual variation. Such is especially the case in the 

 genua Prodelphinus, in which the species may be as few as three or four 

 or as many as twenty or twenty-five. 



Under these circumstances there is no escape from a very unpleasant 

 dilemma. If a new species is erected, there is constantly a suspicion 

 that it is identical with some one ))reviously described from the skull ; 

 while, on the other hand, if the newly acquired si)ecimen is referred to 

 a species already in the literature, there is always the possibility that 

 if the external characters of the latter were known they would prove 

 the two to be distinct. It is seldom that cetologists have the o])por- 

 tiKiity to compare large numbers of individuals of the same species 

 in ;i fresh state, except in the case of such forms as GloMocephalus, of 

 which large schools are frequently stranded. It is imperative that we 

 should make careful .study of such material, and from the results of such 

 S. Mis. 36, }n. L' lil 



