1871.] MR. HARPER PEASE ON POLYNESIAN LAND-SHELLS. 455 



above genus. I note that acetabulum, Pse., should be compared 

 to Jicta, Pse., rather than obolus, Gld., as is done by Dr. Pi'eiffer. 

 I add the following new species : — 



Endodonta celsa, Pse. 



T. orbicularis, solidiuscula, late umbilicata, tenuissime radialim 

 creberrime striatula, rufo et albido pallide tessellata ; spira elevata, 

 apice obtusiusculo, nucleus rufescenti-fascus, sutura bene imprcssa ; 

 an/r. 7, convexi, interdum concentrice elevato-striati, rarissime 

 sulcati aut angulati, ultimas ad peripheriam obtuse anyulatus, 

 subtus rotundatus ; apertura obliqua, fere circularis, lamella 

 unica in anfr. penultimo munita, 



Diam. 7, alt. 3i mill. 



Hub. Insula Raiatea. 



Genus Microcystis. 



Microcystis, Beck, Index Molluscorum, 1837, p. 2. 



Dr. Beck enumerates six species in illustration of the above genus, 

 three inhabiting the West Indies and three Polynesia. The former 

 are H. cubensis, ¥fr.=trifaciella, Beck (also the type of the genus 

 Cystycopsis, Morch), //. pellicula, Fer., locality doubtful, but of 

 West-Indian form, and H. pictella, Beck, which remains undeter- 

 mined. These species are globose in shape, ornamented more or less 

 with coloured bands, of a West-Indian type -well-known to collectors. 

 ^ The Polynesian species are H. omatella, Beck, adamsii, Pfr. = 

 filiceti, Beck, and amcenula, Beck, to which I have lately added a 

 beautiful little species from the Marquesas Islands, viz. marquesana, 

 Pse. The above are much smaller than the West-Indian species, and 

 not so globose, excepting the last, and will not, in my opinion, prove 

 to be congeneric with them. They stand as anomalies in the Poly- 

 nesian fauna, being confined to islands in the extreme easterly por- 

 tion of Polynesia, and are not represented elsewhere. 



It is not improbable that the three species cited by Dr. Beck from 

 Polynesia are varieties of one, as they are all reported from Rapa, 

 a very small island (but 6^ miles long) in the Austral group, about 

 400 miles south of Tahiti/ 



Dr. Pfeiffcr credits adamsii, Pfr., to both Rapa and Pitcairn, 

 which is probably an error. If it occurs at Pitcairn, it is without 

 much doubt distinct from Dr. Beck's species. 



Authors have lately extended this genus to embrace a variety of 

 forms, especially a large group of thin, fragile, glassy species, widely 

 distributed over the Polynesian and Papuan Islands, and extending 

 to Australia.^ They appear to have overlooked the fact that Dr. 

 Beck recognized them as being distinct from Microcystis, and ar- 

 ranged them under the generic name of 



Helicopsis, Beck. 



It was injudicious on the part of Dr. Beck to adopt the above 

 name, as it had been used previously by Fitzinger, although the 



