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Show 1871.] MR. HARPER PEASE ON POLYNESIAN LAND-SHELLS. 465 Genus CHONDRELLA, Pse. Typus, Cyclostomaparvum, Pse. P. Z. S. 1864, p. 674. Testa globoso-conica, tenuiuscula, striata, imperforata, vel ; apertura fere circularis; peristoma simplex, tenue, late disjunctis; columella callo appresso, late induta, locum umbilici tegens. Animal tentaculis nullis, oculis supra caput immersis. Operculum testaceum, solidiusculum, pallidum, nitidum, oblongo-ovatum, latere dextro fere recto, utrinque rotundatum; planum, leevigatum, nucleo obsoleto, marginibus anterioribus lateralibus angulatis; subtus vix concavum, margine rotunde quasi costato. The above genus is peculiar in all respects, animal, shell, and operculum. It should be classed with Helicinidee. It is widely distributed over the islands of Southern Polynesia. Most common at the Hervey group, where Mr. Garrett has had ample opportunity of examining the animal alive. It has positively no tentacles, the eyes being immersed on the head in the situation usually occupied by tentacles. Cyclostoma minutissimum, Sow., the generic position of which has been undecided, belongs to this genus. It inhabits Pitcairn Island. Genus PALAINA, Semp. Palaina, Semp. Journ. de Conch. 1865, p. 291. Pupoidea, Pse. Am. Journ. Conch. 1865, p. 289. The two genera above are no doubt synonymous. As there appears to be a difference of opinion as regards the relation of this genus to those of the Diplommatinacea, by reason partly of a want of knowledge of the characters of its operculum, I furnish the description of that of P. scalariformis, Pse., inhabiting the Caroline Islands. Operculum membranaceum, circulare, multispirale; anfr. 4-5, accrescentes, sutura lineari; extus nitidum, medio depresso-anfr. ultimus rotundatus, margine tenui; subtus vix The outer side is regularly concave to the last whorl, which is rounded, so that the operculum when laid down would rest on its margin. It requires repeated efforts and careful manipulation to separate an operculum, an eighth of a millimetre in diameter, from the animal. If macerated in water until the animal matter becomes soft, the operculum is liable to fall to pieces ; while it is impossible to separate it from the animal in a dried state. I have been successful in obtaining the opercula of all the genera inhabiting Polynesia, excepting Electrina, Gray, of which I have seen no specimens. Genus HELICINA, Lam. Under this genus I merely record the following descriptions aud synonyms. * PROC. ZOOL. Soc-1871, No. XXX. |