Tag Archives: Helenoconcha

Helenoconcha polyodon (Sowerby)

Many-toothed Saint Helena Snail (Helenoconcha polyodon)

The Many-toothed Saint Helena Snail was described in 1844 based on subfossil shells that were collected from a place named Sugarloaf Quarry on the island of Saint Helena.

The species’ author gives some information about the form of the shells.:

“This is the most widely umbilicated of all the species of Patula from St. Helena, and this feature alone is sufficient to distinguish it from the rest. The whorls also, in adult shells eight to nine in number, enlarge very slowly. The striae are fine, regular, arcuately oblique above, and slightly wavy on the last whorl. There are three parietal lirae extending far within the aperture, of which the upper and lower are nearly always double. The plicae within the outer lip are almost invariably (in adult shells) seven in number, subequidistant, but not of equal thickness, two or three towards the columella being stouter than the rest, which are slender and extend some distance within.” [1]

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References:

[1] Edgar A. Smith: On the land-shells of St. Helena. Proceedings of the Zoological Society of London. 1892: 258-270

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Depiction from: ‘G. W. Tryon; H. A. Pilsbry; a.o.: Manual of Conchology. Second Series: Pulmonata Vol. 8, Helicidae Vol. 6. 1892’

(public domain)

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edited: 29.05.2021

Helenoconcha leptalea (Smith)

Slender Saint Helena Snail (Helenoconcha leptalea)

The Slender Saint Helena Snail was described in 1892, apparently on the basis of subfossil shells that were recovered from the so-called Sugarloaf Quarry on the island of Saint Helena. 

The shells of this species are much smaller than those of the closely related Many-toothed Saint Helena Snail (Helenoconcha polyodon (Sowerby)); they were flatter, much more finely striated and differed furthermore by their oral armature. [1]

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References:

[1] Edgar A. Smith: On the land-shells of St. Helena. Proceedings of the Zoological Society of London. 1892: 258-270

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Depiction from: ‘G. W. Tryon; H. A. Pilsbry; a.o.: Manual of Conchology. Second Series: Pulmonata Vol. 8, Helicidae Vol. 6. 1892’

(public domain)

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edited: 29.05.2021

Helenoconcha sexdentata (Smith)

Six-toothed Saint Helena Snail (Helenoconcha sexdentata)  

The Six-toothed Saint Helena Snail was described in 1893, as its name implies, it is, or rather was, endemic to the island of saint Helena.

“This species agrees rather closely with P. pseustes, Smith, in respect of the dentition of the aperture. The palatal lamella, however, in that species is considerably stronger, and the form of the shell is very different. P. cutteri has two similar parietal lamellae, only two basal denticles, and no palatal lamella. In other respects it appears to be very similar, but a trifle larger. Watercresses (Nasturtium officinale) among which it is stated by M. Eudel [M. Emile Eudel, the collector of this species] that this species occurs, are said to be “very common in the ravines and along the mountain streams and ponds.”.” [1]

The shells reach sizes of about 0,3 cm in diameter. 

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The Six-toothed Saint Helena Snail was apparently still found alive when it was described; it is nevertheless now considered extinct. [1]

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The species of this genus, as well as basically all of the Saint Helena Gastropoda species, are in urgent need of a proper revision!

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References:

Edgar A. Smith: Descriptions of two new species of Patula from St. Helena. The Conchologist 2(7): 164-165. 1893

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Depiction from: ‘Edgar A. Smith: Descriptions of two new species of Patula from St. Helena. The Conchologist 2(7): 164-165. 1893’

(public domain)

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edited: 29.05.2021