1835.] DISTRIBUTION OF THE SHELLS. 375 



terrestrial Amblyrhynchus 'and the groups of the marine species 

 basking on the coast-rocks of every island we must admit that 

 there is no other quarter of the world where this Order replaces 

 the herbivorous mammalia in so extraordinary a manner. The 

 geologist on hearing this will probably refer back in his mind to 

 the Secondary epochs, when lizards, some herbivorous, some car- 

 nivorous, and of dimensions comparable only with our existing 

 whales, swarmed on the land and in the sea. It is, therefore, 

 worthy of his observation, that this archipelago, instead of pos- 

 sessing a humid climate and rank vegetation, cannot be considered 

 otherwise than extremely arid, and, for an equatorial region, 

 remarkably temperate. 



To finish with the zoology : the fifteen kinds of sea-fish which 

 I procured here are all new species ; they belong to twelve genera, 

 all widely distributed, with the exception of Prionotus, of which 

 the four previously known species live on the eastern side of 

 America. Of land-shells I collected sixteen kinds (and two marked 

 varieties), of which, with the exception of one Helix found k at 

 Tahiti, all are peculiar to this archipelago: a single fresh- water 

 shell (Paludina) is common to Tahiti and Van Diemen's Land. 

 Mr. Cuming, before our voyage, procured here ninety species of 

 sea-shells, and this does not include several species not yet speci- 

 fically examined, of Trochus, Turbo, Monodonta, and Nassa. He 

 has been kind enough to give me the following interesting results : 

 Of the ninety shells, no less than forty-seven are unknown else- 

 where 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 inhabit the western coast of America, and 

 of these eight are distinguishable as varieties; the remaining 

 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 

 occurring 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 conchological 

 provinces ; but at the Galapagos Archipelago we have a halting- 

 place, where many new forms have been created, and whither 

 these two great conchological provinces have each sent several 

 colonists. The American province has also sent here representa- 



