ON MOLLTJSCA OF THE WEST COAST OF NORTH AMERICA. 681 



Ajnerican waters, whicli have bequeathed some species uow flourishing, and 

 others dying-out, to the existing seas. The present faunas of West America 

 hre perhaps the most isolated on the surface of the globe ; yet, if we knew 

 the ancestry of each specific form, we might find some first appearing with man 

 on this planet, others first living even in historic times, others tracing their 

 descent from remote periods, and it may be very distant localities, in the ages 

 of the Miocene, possibly even of the Eocene oceans. These suppositions are 

 not set forth as theories, but simply to guard against interpretations of facts 

 based on conclusions which may be only the results of our necessarily 

 imperfect information. 



123. With regard to forms offering local peculiarities sufiicient to dis- 

 tinguish them from correlative forms oifering equal peculiarities in some other 

 fauna, we are by no means warranted in assuming that these have sprung 

 from different creations. If a race of men, migrating to a new continent, in 

 a very few generations, or even in the next, develope an essentially different 

 phjsique, it is fair to conclude that molluscs, borne by a change of currents to 

 a distant region, or steadily migrating to the extreme limit of their con- 

 ditions of Hfe, will also change their appearance. If the publication of the 

 " Darwinian Theory " has had no other effect, it has at least checked the pro- 

 pensity to announce " new species " for difi'erences which may fairly be re- 

 garded as varietal. It must also be borne in mind, that if the views of Mr. 

 Darwin be only a theory, such also is the name required for the prevalent 

 opinion of separate creations for all diverse forms. What indeed can we 

 possibly know of the mode of original creation of a single species "? We can 

 onlj- prove that one or the other supposition best explains a certain class of 

 facts. It is not necessaiy for a working naturalist to commit himself to an 

 exclusive belief in either of these theories. He may perhaps best explain 

 some facts by the doctrine of separate creation, others by that of natural 

 selection. In either case it is his duty to trace-out, as far as possible, the 

 limits as weU as the powers of variation in every living form, and to guard 

 against seeing that only which accords with his prevailing belief. 



124. The study of European shells, as they exist in Norway, in Britain, in 

 the Mediterranean, at the Canaries, or as they appear at different depths 

 and stations in our own seas, still more as they occur in the widely separated 

 periods of the later and middle tertiary ages, is an excellent preparation for 

 the examination of either recent or fossil faunas in districts where our know- 

 ledge is fragmentary and unconfirmed. It may be safely stated that there are, 

 in the American waters, many tropical forms from the West Indies and the 

 Pacific shores, some temperate forms from California and the Atlantic, and 

 many sub-boreal species in the Vancouver district and the European seas, 

 not differing from each other more or even so. much as forms universally 

 allowed by malaoologists to have had a common origin from Britain and the 

 Mediterranean, from the Red and the Coralline Crag. 



12-5. It is interesting to observe that, notwithstanding the probable con- 

 nexion of the oceans through the Eocky Mountains during the Miocene age, i 

 there is extremely little similarity between the special temperate faunas of 

 East and West America. Not a single species has yet been proved identical, 

 and the aUied forms are but few in number. They appear as follows : — 



Californian species. U. S. Atlantic species. 



Clidiophora punctata. 

 Lvonsia Californica. 

 !^facoma inconspicua, 

 Angulus modestus. 

 Baeta undulata, I B. canaliculata, 



167 



C. trilineata (.'' = n(i=:uta). 

 L. nivalina=)Floridaaa. 

 M. fusca. 

 A. tener. 



