ON MOLLUSCA OF THE WEST COAST OF NORTH AMERICA. 361 



This list (which is believed to be very accurate in all respects except 

 Modiola capax, which is not included in the analysis) contains 20 land 

 and freshwater shells, all of which are believed to be peculiar to the islands, 

 except a Helix found at Taiiiti, and a small Paludina, common to Tahiti, 

 and Van Diemen's Land {Darioin). Of the 90 marine shells analysed by 

 Darwin, 47 Avere not known elsewhere; 25 inhabited the West coast of 

 America, 8 being distinguishable as varieties; the remaining 18 having been 

 found by Mr. Cuming in the Low Archipelago, and some of them also at 

 the Philippines, Prof. Forbes, speaking of the Galapagos in the 'Mem. 

 Geol. Soc. Gr. Br.' vol. i. p. 402, note, says, "We have distinct systems of 

 creatures related to those of the nearest land by representation or affinity, 

 and not by identity." The latter word does not hold good of the sea shells; 

 for there are already known 111 species at the Galapagos, of which 55, or 

 nearly one half, are American shells; of these 25 inhabit the Gulf; 22 

 have already been taken in Central America ; 38 are found at Panama ; but 

 only 1 1 from the parallel latitudes in South America. Only 4 bivalves are 



