ALEUTIAN PROVINCE. 373 



Saxidomus giganteus. S. Telliua lutea. A. nasuta. S. 



Petricola cyliudracea. S. „ edentula. A. 



„ gibba. S. Lutraria maxima. S. 



The influence of the Asiatic coast-current is shewn in the presence of two 

 species of Hadotis, whilst affiuity with the fauna of W. America is strongly- 

 indicated by the occurrence of Patella {scun-a), three species of Crepidula, 

 two of Fissurella, and species of Bullia, Placunomia, Cardita, Saxidomus, 

 and Petricola, which are more abundant, and range farther north than their 

 allies in the Atlantic. 



Provinces on the Western coast of America. 

 The mollusca of the Western coast of America are equally distinct from 

 those of the Atlantic and those inhabiting the central parts of the Pacific. 



Mr. Darwin states in his Journal (p. 391) that "not one single sea-shell 

 is known to be common to the Islands of the Pacific and to the west coast of 

 America," and he adds that " after the comparison by Messrs. Cumiug and 

 Hinds of about 2000 shells from the Eastern and Western coasts of America, 

 only one single shell was found in common, namely the Purpura patula, 

 which inhabits the West Indies, the coast of Panama, and the Gallapagos." 

 Even this single ideatification has since been doubted. Mr. Cumiug, who 

 resided many years at Valparaiso, did not discover any West India species on 

 that coast, and M. D'Orbigny makes the same observation. On the other 

 hand M. Morch of Copenhagen says he has received Tellina opercnlata aud 

 Mactra alata from the west coast and also from Brazil ; and j\T. Deshayes 

 gives the following extraordinary ranges in his " Catalogue of Venerida in 

 the British Museum :" 



Ai-temis angulosa, Philippines — Chile. 

 Cytherea umbonella, Eed Sea— Brazil. 



„ maculata, W. Indies— Philippines, Sandwich. 



„ circinata, West Indies — West coast America. 

 In these instances there is doubtless some mistake, either about the 

 locality or the shell. As regards the last, Mr. Carrick Moore has shown that 

 the error has arisen from confounding the Cytherea alternata of Broderip 

 with C. circinata of Born. M. D'Orbigny collected 628 species on the coast 

 of S. America,— 180 from the eastern side, aud 447 from the Pacific coast, 

 besides the Siphonaria Lessonii which ranges from Valparaiso in Chile to 

 Maldonado on the coast of Uruguay.* These shells belong to 110 genera, 

 of which 55 are common to both coasts, while 34 are peculiar to the Pacific, 

 and 21 to the Atlantic side of S. America; an extraordinary amount of 

 diversity, attributable partly to the different character of the two coasts — the 



♦ The dispersion of this coast shell may perhaps have taken place at the time 

 when the channel of the river S. Cruz formed a strait, joining the Atlantic and 

 Pacific oceans, like that of Magellan. (Darwin, p. 181.) Mr. Couthouy makes 3 sp. 

 S. iessonjj, nearly smooth, Atlantic coast; S. antarctica, ribbed. Pacific coast; and 

 •S. lateralis, thin, oblique, Fuegia. 



