LITTORAL DISTRICTS. 221 



LITTORAL DISTRICTS. 



NoRTn Pacific (PI B) and Boreal American Districts (PI. A). 



The North Pacific District extends from the Sea of Okhotchk to the Gulf 

 of Georgia, and some of its species even to San Diego. Echinarachius excen- 

 tricus is found on the American and Asiatic sides of the Pacific, and in the 

 same localities as the North Circumpolar species (Pi. B), S. Drobachiensis. 



E. excentricus extends to San Diego, and as far as the Gulf of Georgia is 

 found associated with E. parma, an eminently boreal American (PI. A) spe- 

 cies, which however goes far south on the Asiatic side of the Pacific, even 

 to the East India Islands, if we can credit the localities, across the whole 

 of the Japanese and Chinese Districts, and is besides eminently characteristic 

 of the northeastern coast of North America associated with the North Cir- 

 cumpolar species S. Drobachiensis. 



Californian, Panamic, and "West South American Districts. 



The true Californian (PI. B) fauna, extending from the Santa Barbara Chan- 

 nel Islands to the Gulf of Georgia, lapping the North Pacific and the Circum- 

 polar species, is poor in species, Strongylocentrotus franciscanus and S. 

 purpuratus being thus far the only species known on that extensive stretch 

 of coast strictly peculiar to it. The southern boundary of this fauna merges 

 into the northern extremity of a more varied coast, the Panamic (PL B), 

 extending from the northern part of Peru to the Santa Barbara Channel, 

 though many of the species have thus far not been traced beyond Cape St. 

 Lucas. Like the Japanese and Chinese fauna, it is made up of generic ele- 

 ments from the adjoining districts, the Indo-Pacific, Peruvian, Panamic, East 

 Indian, Australian, West Indian, all being represented, the former by the 

 presence of such species as Astropyga pulvinata, Toxopneustes pileolus, Lo- 

 venia cordiformis, and Metalia maculosa ; the Peruvian by the presence of 

 Agassizia, and the species of Arbacia ; the strictly Panamic species being for the 

 greater part representatives of the West Indian types ; the East Indian hav- 

 ing in common a species of Echinanthus, and the Australian the genus Cen- 

 trostephanus. The (Peruvian) West South American (PI. A) fauna extend- 

 ing from the northernmost part of Ecuador, lapping the Panamic District, 

 extends to the southernmost limit of Chili, two of the species even ex- 



