202 AMERICAN JOURNAL 



the necessity for this friendly criticism would not have arisen." 

 With respect to the views entertained by Professor Adams, 

 that no species could be common to the Atlantic and Pacific 

 Oceans, it may be mentioned as an interesting fact, that he 

 departed from his theory as regards Crejpidida unguiformis, 

 Lam."^ As to this species the Professor observes: — 



"This shell is well calculated to confound the popular no- 

 tion of species. We have now before us many perfect spe- 

 cimens from Sicily, from Massachusetts, from Jamaica, and 

 from Panama, all of which, with the exception of the Medit- 

 erranean shells, we collected in person." 



"So far, at least, as the shells are concerned, it seems neces- 

 sary to admit that they all may be comprised in one species; 

 or to maintain that individuals, which cannot be distinguished 

 from each other, belong to different species, because it is proba- 

 ble that they descended from distinct original stocks. But if 

 we admit that each species in the animal kingdom was intro- 

 duced by the creation of many original stocks, then the fact 

 before us becomes intelligible and very uncommon in only one 

 particular, viz: that the original individuals of a single spe- 

 cies were created in very distant zoological provinces." — "Pa- 

 nama Catalogue," p. 231. 



After the foregoing brief review of the work of Professor 

 Adams on the Panama Shells, and reference to his opinions as 

 to the origin and distribution of species, it will not be out 

 of place to state the results of study and research devoted 

 since his death to the subject of the Mollusca of the west coast 

 of America. 



Carpenter, in his before mentioned "Eeport" of 1856, enu- 

 merates 35 species "regarded as identical between the Pacific 

 and Atlantic," 34 "which may prove to be identical," 41 

 "really separated, but by slight differences," and 26 species 

 "analagous, but quite distinct," remarking, that probably 

 those lists will hereafter be greatly extended. 



The same author, in his "Supplementary Eeport," ("Report 

 of Brit. Assoc," 1864,) has some extremely valuable remarks 

 with respect to the marine fauna of the west coast, some of 

 which may thus, but in his own words, be shortly stated : — 



"With regard to the tropical fauna, the researches at Cape 

 St. Lucas and in the interior of the Gulf of California, though 

 leaving much to be desired, bear out the general conclusions 

 arrived at in paragraphs 78 — 87 (of the Report of 1856). The 

 evidence for the identity of specific forms on the Atlantic and 

 Pacific sides of Central America has been greatly confirmed. 



* See Carpenter's remarks in "Cat. of Reigen Collection, Brit. Mus.," 

 1855 — 7, p. 285, and in his "Review," referred to in the text. 



