page 160
ON A NEW REVERSED TASMANIAN HELIX. HELIX WELDII.
BY THE REV. J. E. TENISON-WOODS, F.G.S., COR. MEM. ROY. SOC., SYDNEY AND TASMANIA, AND OF LIN. SOC., New South Wales.
[Read October 9th, 1876]
A very few years ago the island of Tasmania was regarded as being poor in land shells, but thanks to the zeal and activity of many naturalists, especially Messrs. Legrand, Atkinson and Petterd, the number of species brought to light is now very large. If the island cannot take a leading position for the number and peculiarity of its forms it has by no means an insignificant one. Up to a recent period the description of the species were scattered over an immense number of scientific works according as they had been described by various observers in different countries. Within the last few years Mr. W. Legrand has published a monograph of all the then known land shells, accompanied with extensive notes on the habits, and very excellent figures of the newer species. What gave the work a greater value was that it was for the most part privately printed by the author, the whole of the work being done by his own hand. This work leaves but little to be desired, though new species are of frequent occurrence. It is remarkable that our land shells are entirely distinct from the Australian fauna, except in a few doubtful cases, and some of the forms are beautiful and peculiar in a way that is so marked as to enable us to call it "Tasmanian." I have now to bring under the notice of the Society a new species of Helix which has the additional singularity of being a reversed shell. Helices with a sinistral whorl are uncommon. Out of the vast number hitherto made known, including every variety of form in the genus, I believe I am right in stating that very few more than a dozen are reversed, and this sinistration, if I may be allowed to coin a word, is not confined to any particular section of the genus so as to elevate it to generic importance. It is remarkable, however, that hitherto as far as I am aware it has been only found in Helices of China, the Indian Archipelago, and in the Indian Peninsula. It is, I may say, a tropical peculiarity, but, at least, no such form has as yet been hitherto found in the Southern Hemisphere. The present species is very small, confined, as far as we know, to one restricted locality on the north-west side of the island. It was found by Mr. W. F. Petterd. I have done myself and the Society the honour of dedicating it to Her Majesty's representative in the colony, His Excellency the Governor, F. A. Weld, Esq., C.M.G. The following is the diagnosis:—
HELIX WELDII. n.s. H.t. Minuta sinistrorsa, anguste umbilicata, turbinato-discoidea, tenuiuscula, nitente, striis confertis,
page 161
sublente tantum bene conspicuis longitudinaliter impressa; pallide corneo-lutea, unicolor, translucent; spira leviter conica, apice prominulo, obtuso; sutura valide impressa; anfr. 6 1/2, convexi, sensim accrescentes, embryonales 1 1/2, albidi, ultimus rotundatus, basi subplanatus; apertura rotundato-lunaris basali, concolor; peristoma simplex, acutum, corneum, marginibus ab umbilico usque ad 1/2 ultimi anfractus disjunctis; columella brevi. Diam. maj. et min 1 1/2; alt. 1 1/4 mil. Habitat in vicinio civitatis Stanley dictoe, Tasmanioe. Obs. Sp. valde minuta et sinistrosa, forma vero et colore speciebus multis Tasmanioe incolantibus sat proxima.
Shell minute, sinistral, narrowly umbilicate, turbinately discoid, rather thin, shining, with close small longitudinal striae, which are only visible under the lens; pale yellowish horn and of uniform color, translucent; spire slightly conical; apex a little prominent, obtuse; suture validly impressed; whorls 6 1/2, convex, gradually increasing, embryonal whorls 1 1/2, whitish; last whorl rounded and somewhat flattened, of uniform color; peristome simple, acute, horny; aperture roundly lunate, margins of the peristome separated from the umbilicus to half the height of the last whorl, columella short.
Mr. Petterd notes with reference to this shell. "This small and reversed Helix I have only observed at the foot of the high rocks about Stanley, Circular Head, where I collected it with a few other species of Helices on the surface of blocks of rocks that are overgrown with a thick mass of entangled vegetation. It is extremely abundant and generally in clusters. I have collected some hundreds of specimens. The reversed form is very constant."