ON MOLLUSCA OF THE WEST COAST OF NORTH AMERICA. 167 



these closely allied species has been decided by their anatomy, we believe 

 it to be perfectly safe to adopt this axiom, — that species, whencesoever 

 derived, possessing the same characters, are identical. We view this to be a 

 more rational course than to consider them to be the analogues of each 

 other; a convenient but very indefinite mode of expression, which may be 

 used to cover every degree of similitude, from a general analogy to a close 

 affinity hardly admitting of distinction*.'' 



21. As far as facts already ascertained justify us in drawing any conclu- 

 sions, it would appear that while the shells in each of the great provinces 

 throughout the world are in the main remarkably distinct from each other, 

 there are in each fauna (1) many shells which are parallel with those from 

 other seas ; (2) some which are nearly ubiquitous, and often extend far 

 back in geological age ; and (3) others which, though by no means widely 

 diffused, reappear very unexpectedly in far-distant seas. Thus Philippi and 

 Hanley quote shells common to the Mediterranean and Australia; Mr. 

 Cuming finds the British Lucina borealis and Nassa incrassata at the Philip- 

 pines ; and even Mr. Hinds can trace no difference between a JYecera of the 

 China Seas and the European N. costellata. As to the line of demarcation 

 between species and varieties, that must remain in many cases a matter of 

 individual opinion. Those who, with Prof. Adams, can speak of the different 

 species of Man (Conch. Contr. p. 87 ; a view more congenial to the "pe- 

 culiar institution" of the stripe-flagged United States than to the readers of 

 Pritchard's Physical History), may be expected to constitute species of 

 shells on characters which to others will appear of secondary importance; 

 while those who have been in the habit of examining large multitudes of 

 specimens will take a larger view of the probable extent of specific variation. 

 These differences will be taken into account in comparing the works of one 

 naturalist with another. 



22. Having thus shown the grounds of caution in using the materials by 

 which a knowledge of local faunae is to be derived, we proceed to examine, 

 one by one, the sources of information which have been discovered with 

 regard to the Mollusca of the two great divisions of the West N. American 

 fauna. The localities to which they principally refer may be arranged as 

 follows : — 



I. Boreal Fauna, a. Circumpolar. Icy Cape, lat.f 70"5°. Behring's Straits, on 



the Arctic circle. " Bearing Sea." 



b. Asiatic. Sea of Okhotsk, with the Schantar Is., 55°. Kurule Is., from Japan 

 to Kamtschatka. Petropaulovski, 52' 5°. Cape Lopatka, 51° : from which 

 the Aleutian Is. extend to 



c. American. Prom. Aliaska. Those most explored are, Is. Kodiak, 57°; Oona- 

 lashka, 54° ; Atcha, 53°. Norfolk Sound in King George's Archipelago. Sitcha, 

 58°, in the parallel of the Hebrides. 



II. Temperate Fauna, a. Oregon. (Parallel of France.) Vancouver's Is. 49°-51°, 



with Nootka Is. and Sound; separated on the south from the mainland (of 

 which the extreme point is Cape Classet) by the Straits of San Juan de Fuaco, 

 at the S. end of which is Ft. Nisqually, 47°. At the mouth of Columbia River 

 are Townsend and Discovery Harbour, 46°. Up the river is Ft. Walla Walla. 

 R. Willamette flows upwards into the R. Columbia, near Ft. Vancouver, 46°. 

 b. Upper California. (Parallel of the Mediterranean.) " Colonie Russe," or Bo- 

 degas, 38°. San Francisco and R. Sacramento, 37'5°. Monterey, 365°. Sta 

 Barbara, 34°. Is. Catalina, 34°J. 



* Fide Prof. Agassiz on the " Geographical Distribution of Animals," in the ' Christian 

 Examiner/ Boston, March and July 1850. 

 •f" The degrees are only given approximately, 

 j Another Is. Catalina is in the Gulf. 



