DISTRIBUTION OF SHELLS. 163 



no less than forty-seven are unknown elsewhere : a 

 wonderful fact, considering how widely distributed 

 sea-shells generally are. Of the forty-three shells 

 found in other parts of the world, twenty-five in- 

 habit the western coast of America, and of these 

 eight are distinguishable as varieties ; the remain- 

 ing eighteen (including one variety) were found by 

 Mr. Cuming in the Low Archipelago, and some of 

 them also at the Philippines. This fact of shells 

 from islands in the central parts of the Pacific oc- 

 curring here deserves notice, for not one single 

 sea-shell is known to be common to the islands of 

 that ocean and to the west coast of America. The 

 space of open sea running north and south off" the 

 west coast separates two quite distinct conchologi- 

 cal provinces; but at the Galapagos Archipelago 

 we have a halting-place, where many new forms 

 have been created, and whither these two gi'eat 

 conchological provinces have each sent several col- 

 onists. The American province has also sent here 

 representative species, for there is a Galapageian 

 species of Monoceros, a genus only found on the 

 west coast of America ; and there are Galapageian 

 species of Fissurella and Cancellaria, genera com- 

 mon on the west coast, but not found (as I am m- 

 formed by Mr. Cuming) in the central islands of 

 the Pacific. On the other hand, there are Galapa- 

 geian species of Oniscia and Stylifer, genera com- 

 mon to the West Indies and to the Chinese and 

 Indian seas, but not found either on the west coast 

 of America or in the central Pacific. I may here 

 add, that after the comparison by Messrs. Cuming 

 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 Galapagos. We have, there- 



