450 MR. HARPER PEASE ON POLYNESIAN LAND-SHELLS. [May 2, 



Hogoleu. The genus Registoma is represented by a single species. 

 All the above East-Indian forms occur on the most westerly islands, 

 which have not been thoroughly explored ; I anticipate that, when 

 searched, they will yield a much larger proportion of Polynesian 

 species, for the reason that these are of small size, and have escaped 

 the notice of inexperienced collectors. 



Passing south over the Tarawan Islands (Kingsmill), all of which 

 are low atolls, we arrive at the Samoas, the nearest group in Southern 

 Polynesia to the Papuan Islands ; it has yielded but a small number 

 of species, although it has been explored by several persons within 

 the past ten years*; they are all peculiar or of Polynesian types. 

 Going on east to the Tahitian, Hervey, Austral, Paumotus, and Mar- 

 quesan groups, comprising over one half of all the Polynesian islands, 

 we find them inhabited by pure Polynesian forms. 



The genus Partvla here attains to its highest development ; also 

 Pitys and other genera of Helicince. All the operculated genera, 

 with the exception of the cosmopolitan genera Helicina and Trunca- 

 tella, are peculiar. The type of Omphalotropis, Pfr., does not extend 

 to this part of Polynesia ; but the genus is represented by several 

 peculiar varieties which I have distinguished under the subgeneric 

 names of Scalinella, Atropis, and Cyclomorpha. 



The genus Diadema, Pse., is confined to the Hervey group ; and 

 Chondrella, Pse., is widely spread over the several islands. Two of 

 the genera characteristic of the Polynesian fauna appear to have 

 passed over to the Papuan Islands, viz. Partula and Pitys ; of the 

 former, nineteen species have been described from those islands. 

 With one or two exceptions they are of simple bulimiform shape, and 

 may not, at least all, prove to belong to the genus. Thirty-five or 

 more species of Helices have been described from the Papuan Islands, 

 Australia, New Zealand, and Tasmania, under the genera Patula, 

 Discus, &c, which are nearly related to the Polynesian genus Pitys. 

 They are generally more planorboid in shape, with the aperture open 

 and not laminate or dentate ; their relation to the genus Pitys cannot 

 be determined until the animals are examined and compared. 



It appears, therefore, that while a few East-Indian types have 

 entered and extend a short distance into Western Polynesia, as 

 might be expected from their near contact on the south, the Poly- 

 nesian genera have passed over to the Papuan Islands. 



The Hawaiian Islands, on the northerly boundary of Polynesia, 

 present several peculiarities in both their marine and land fauna, as 

 might be supposed from their isolated position. Over two thirds of all 

 the land-shells belong to the Helicterince, all of which are confined 

 to that group of islands, as also the genera Oarelia and Catinelln. 

 The several genera of Helicince are common with Southern Polynesia. 



The only operculated genus is Helicina; while on the islands of 

 Southern and Western Polynesia no less than sixteen occur. It is 

 also the only locality in which the genera Blauneria, Pedipes, and 

 Ophicardelus of the Melampinse have been discovered. 



* The Saraoan Islands, in proportion to their size, are inhabited by a few 



more than one quarter of the number of speeies found at the Tahitian. 



