Truncated Saint Helena Awl Snail (Chilonopsis subtruncatus)
This species was already extinct for several centuries when it was described for science in the year 1892.
The shells reached a size of about 3 cm in diameter.
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edited: 21.03.2018
Blofeld’s Saint Helena Awl Snail (Chilonopsis blofeldi)
Most members of the genus Chilonopsis (eight species are known) were probably extinct shortly after the establishing of settlements on Saint Helena, in the early 16th century.
The final extinction of so many endemic snail species of Saint Helena was probably caused by the nearly complete destruction of the native vegetation by farmers and their domestic animals.
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edited: 21.03.2018
Turton’s Saint Helena Awl Snail (Chilonopsis turtoni)
This variable species was described in the year 1892.
Turton’s Saint Helena Awl Snail was obviously still extant in the middle of the 19th century, since some individuals were found at the higher elevations of Saint Helena, crawling among the remnants of the native vegetation.
The shells reached a height of about 1,7 cm. [1]
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References:
[1] Edgar A. Smith: On the Land-Shells of St. Helena. Proceedings of the Zoological Society of London 258-270. 1892
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edited: 21.03.2018
Dark Saint Helena Awl Snail (Chilonopsis melanioides)
This species was described in the year 1878 based on specimens that were collected at Diana’s Peak, Saint Helena’s highest point, at an elevation of about 600 m.
The shells reached a height of 0,9 to 1,1 cm.
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The species was still extant, when it was discovered, but nevertheless it was already in the state of final extinction, see hereto Thomas Vernon Wollaston in the year 1878 (Testacea Atlantica).:
“… though a single living example which was secured by Mr. P. Whitehead in an immediately adjoining locality sufficed abundantly to indicate the modus vivendi of the species, – it having been taken at the roots of one of the damp masses of intermingled moss and grass which pad the base of the perpendicular rocks formed by the excavation of what is known as the ‘Cabbage-Tree Road’. There can be little doubt, consequently, that the S. melanioides will be ascertained to occur in humid places generally along the northern slopes of the ridge below Diana’s Peak.” [1]
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References:
[1] T. Vernon Wollaston: Testacea Atlantica: or the Land and Freshwater Shells of the Azores, Madeiras, Salvages, Canaries, Cape Verdes, and Saint Helena. London: L. Reeve & Co. 1878
[2] Edgar A. Smith: On the Land-Shells of St. Helena. Proceedings of the Zoological Society of London 258-270. 1892
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edited: 21.03.2018
Subplicate Saint Helena Awl Snail (Chilonopsis subplicatus)
The Subplicate Saint Helena Awl Snail was described in 1844 on the basis of subfossil shells that were found in deposits on the island of Saint Helena.:
“Quite distinct from any other known species and of elongate form like the section Peronaeus. The Cochlicopa terebellum of Sowerby, a slightly more slender form, is evidently merely a slight variety in which the plications at the suture, probably through the worn condition of the specimens, appear to be less developed.“ [1]
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The species might very well have survived into quite recent times and probably disappeared only after the arrival of the first human settlers in the 16th century.
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References:
[1] Edgar A. Smith: On the land-shells of St. Helena. Proceedings of the Zoological Society of London 258-270. 1892
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edited: 29.05.2021
Banished Saint Helena Awl Snail (Chilonopsis exulatus)
This species, like all members of the genus, comes from the island of Saint Helena, it was described in the year 1852 based on subfossil shells.
The shells reached a height of ca. 2 cm.
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The species seems to have survived quite long, maybe even until the beginning of the 19th century, Thomas Vernon Wollaston writes hereto in the year 1878 (Testacea Atlantica).:
“My own belief however is that in all probability it was as much subfossilized as are the bleached and still coloured examples of the B. helena, Quoy, which lie scattered loosely in many places on the summit of the Barn; and until further evidence therefore has been adduced, I suspect that it will be safer to treat it as belonging to the extinct fauna of the island, though with the appearance of its having lingeredon (like the B. helena) into comparatively recent times.” [1]
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References:
[1] T. Vernon Wollaston: Testacea Atlantica: or the Land and Freshwater Shells of the Azores, Madeiras, Salvages, Canaries, Cape Verdes, and Saint Helena. London: L. Reeve & Co. 1878
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edited: 21.03.2018
Saint Helena Awl Snail (Chilonopsis helena)
The Saint Helena Awl Snail was described in the year 1833 based on subfossil shells.
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Thomas Vernon Wollaston writes in the year 1878 (Testacea Atlantica).:
“The present Bulimus, which was admirably figured by Quoy in 1833, occurs rather abundantly on the extreme summit of the Barn, and in that immediate neighbourhood, lying loosely on the surface soil, beneath the shrubs of Salsola, &c., – where it has much the appearance of having lived at a comparatively recent period. At all events many of the examples have their colour and outher cuticle completely preserved, – though it is equally true that the majority of them are decomposed, decorticated, and colourless.” [1]
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References:
[1] T. Vernon Wollaston: Testacea Atlantica: or the Land and Freshwater Shells of the Azores, Madeiras, Salvages, Canaries, Cape Verdes, and Saint Helena. London: L. Reeve & Co. 1878
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edited: 21.03.2018
Large Saint Helena Awl Snail (Chilonopsis nonpareil)
The Large Saint Helena Awl Snail is the largest member of its genus, some shells reached sizes of up to 4,7 cm.
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See Thomas Vernon Wollaston in 1878 (Testacea Atlantica).:
“The B. auris-vulpina, which has been brought from St. Helena by almost every naturalist who has visited the island during the last fifty years, appears to be quite extinct; though the comparatively perfect preservation of occasional examples, in which the outher cuticle is hardly destroyed and even the colour is partially traceable, would perhaps imply that it must have lingered on to a somewhat recent period.” [1]
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References:
[1] T. Vernon Wollaston: Testacea Atlantica: or the Land and Freshwater Shells of the Azores, Madeiras, Salvages, Canaries, Cape Verdes, and Saint Helena. London: L. Reeve & Co. 1878
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edited: 21.03.2018