ON MOLT.rSCA OF THF 'WEST COAST OF NORTH AMF.RICA. C81 



American waters, which have bequeathed some species now flouriishing, and 

 olbers dying-put, to the existing soas. The i)resent fuunfis ot West America 

 are perhajjs tlie most isolated on the surface of the globe ; yet, if we knew 

 the ancestry of each specific form, we might find some first api)earing with man 

 en this planet, others first living even in historic times, others tracing tlieir 

 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 ot fiicts 

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

 imperfect information. 



12;}. With regard to forms offering local peculiarities sufficient In dis- 

 tinguish them from correlative forms offering ecjual peculiarities in some other 

 ftiuna, 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 

 2>h>fsi</He, it is fair to conclude that molluscs, borne by a ch.ange of currents to 

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

 ditions of life, will also change their appearance. If the })ublication of the 

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

 pensity to announce " new species" for differences wliich 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 recpiired 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 

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

 facts. It is not necessary 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 nat'.iral 

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

 limits as well 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 ai)pear at diflt rent deptlis 

 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 prei)aration for 

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

 ledge is fragmentarj' and unconfirmed. It may be safelj- stated that there are, 

 in the American waters, many trojiical 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 malacologists to ha%.' had a )mmon origin from Britain and the 

 Mediterranean, from the Red and the Coralline Crag. 



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

 nexion of the oceans through the Rocky Mountains during the Miocene age, 

 there is extremely little similarity between the special tem])erate faunas of 

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

 and the allied forms are but few in niynber. They appear as follows : — 



Californian species. U. S. Atlantic species. 



Clidiophora punctata. 

 Lyonsia Californica. 

 Macoma inconspicua. 

 Angulus niodestua. 

 Kaeta uudulata. 



C. trilineata (? = nnsuta), 



L. (hyalina=jFloridaua. 



M. fusca. 



A. tener. 



K. caualiculuta. 



167 



