460 FAMILY PHOCHXffi. 



have been four periods of unusual fertility in respect to the lit- 

 erature of the Phocidce. The first covers the time of Egede, 

 Cranz, Anson, Steller, and Parsons (1741-1765), and antedates 

 nearly all of the systematic literature of the subject, but for which 

 it formed the ground-work of the early portion. The second 

 (1776-1792) may be termed the period of Fabricius, Schreber, 

 Erxleben, Molina, Ginelin, and Kerr, or that of the early tech- 

 nical writers. The third may be denominated the Encyclopaedic 

 period, covering the work of Desmarest, F. Cuvier, Lesson, Gray 

 (his first general review of the species only), to which may be 

 added (in point of time) Pe"ron, Xilsson, Fischer, and Pallas 

 (1816-1831). During this period originated more than one-half 

 of the synonyms with which the literature of the subject is bur- 

 dened, out of nearly forty names only two representing valid 

 new species. Within this period were published no less than 

 eight mongraphic revisions of the Pinnipeds, prepared by the 

 leading marnmalogists of that time. The fourth period may be 

 regarded as extending from 1837 to 1873, but the different por- 

 tions of this interval were not equally prolific in important gen- 

 eral memoirs. Of special note in the light of a general revision 

 of the subject are those of Nilsson (1837), Gray (1844), Wagner 

 (1846), Gray (1850), Giebel (1855), Gray (1866, 1871, 1873), and 

 Gill (1866). 



CLASSIFICATION. 



As already noted, three subfamilies of the Phocidce are now 

 commonly recognized, while the number of genera admitted by 

 two leading authorities who have recently revised the group is 

 respectively twelve (Gill) and thirteen (Gray), with, in the ma- 

 jority of instances, only a single valid species to each. Nine of 

 OilFs genera are monotypic, while of the others two have two 

 species each. The generic affinities of one the little-known 

 .West Indian Seal have yet to be determined. As will be 

 shown later, only sixteen species can be considered as satis- 

 factorily established. Consequently the question naturally 

 arises whether generic division among the Phocids has not been 

 carried to an excessive degree, and if so, whether the groups 

 termed subfamilies are really entitled to that rank. In the 

 Pinnipedia differentiation, it is true, has been carried to such 

 a degree that not only are the family types sharply circum- 

 scribed, but the species are so far specialized as to form types 

 that at least some naturalists look upon as types of generic, or 

 .at least subgeneric, value. Of the six Otarian genera, four are 



