COMPARISON WITH ALLIED SPECIES. 607 



Differential Characters. In color the Einged Seal is 

 not easily distinguishable from certain phases of the Harbor 

 Seal, but it differs from it in its general form, which is much 

 slenderer, with longer limbs and tail, narrower head, and more 

 pointed nose. The Ringed Seal may, however, be distin- 

 guished externally from both the Harbor and the Greenland 

 Seals by the form of the manus, in which the first digit is the 

 longest, the others successively slightly decreasing. The cra- 

 nial characters, and especially the dentition, differ too widely 

 from those of the Harbor Seal to even require a comparison in 

 the i)resent connection, as do also most of the principal bones 

 of the skeleton (see antea, pp. 565-571). 



The Einged Seal differs externally from the Greenland Seal 

 in its smaller size and in the very different coloration of the 

 adults of the two species. When in the " white coat," and in 

 the earlier spotted stages, coloration often fails to be diagnostic, 

 but they may be distinguished by the character of the manus 

 already given. The dentition of these two species, allowing for 

 the difference in size, is quite similar, although the teeth are 

 relatively (as well as absolutely) larger in Fhoca groenlandica. 

 In the general form of the skull there is also a close resem- 

 blance, although the facial portion is rather more attenuated in 

 F. grcenlandica. The form of the palatal region, however, is 

 widely different in the tAvo, the broad shallow posterior nares, 

 completely di\^ded into two separate passages by a bony sep- 

 tum, and the squarely truncate, instead of deeply emarginate, 

 posterior border of the palatine bones serving at a glance to 

 distinguish P. groenlandica. 



The relationship of Pkocafoetida to the Baikal and Caspian 

 Seals (Phoca sibirica and P. casjnca) is apparently much closer 

 than to any other. The earlier writers, however, as Erxleben, 

 Gmelin, and Pallas, associated them with Phoca rittdina, they 

 forming respectively Erxleben's varieties ;S and y of this spe- 

 cies, and Gmelin's varieties sibirica and caspica. The Caspian 

 Seal was first recognized as a distinct species by ISTilsson in 

 1837, and called by him Phoca caspica. Later its specific dis- 

 tinctness was admitted by Gray (1844), Wagner (1840), and 

 Eadde (18G2). Nilsson was also the first to make known the 

 fact of its much closer resemblance to Phoca fcetida (= P. an- 

 nellata, Nilss.) than to Phoca vitulina.* Wagner arrived at the 



* After detailiug its characters, lie remarks, "Jeder sieht ein, dass diese 

 Form der Ph. annellata viel naher stelit, als der Ph. vituUna. Docli bildet sie 

 ohne alien Zweifel eine von ersterer bestimmt verschiedeue Art : sie ist viel 



