Subgenus Eostrophia

Original Description

"Shell destitute of internal lamellae or denticles.  Maynard has shown that the species of Strophia now living may be separated into three groups by the form and arrangement of the gular laminae or callosities.  But according to him there are none known among recent Strophias, which are entirely destitute of such laminae, like the Miocene forms now under consideration." (Dall, 1890:12).

"Subgenus Eostrophia Dall 1890.

            Shell without axial or parietal laminæ, otherwise as in Strophiops. Fossil of the Older Miocene. Type E. anodonta Dall, Tampa silex beds. Cf. Trans. Wagner Inst., III. 12, August, 1890.

            While Cerion in the broad sense forms a very recognizable group, and one which remounts to a notable antiquity, the divisions above mentioned, apparently constant and easily identified, are of at least as much systematic value as three fourths of the "generic" subdivisions made of late among the Pulmonata, the convenience of which I should hesitate to deny. I have therefore thought it desirable that names should be applied to them, and attention thus invited to the very interesting group under consideration.

            We owe to von Martens (Malak. Bl., VI. 209) the interesting observation, which I have not seen noted elsewhere except by Maynard, that the young shells of Cerion have both palatal and basal denticles in the apertures which in most forms are absorbed later, though in Cerion s. s. they appear, or part of them, to remain permanently present, as shown in the section of C. uva in the accompanying plate. Helix pentodon Mke., appears to have been founded on an immature Cerion in this state.

            It would be a most valuable contribution to the history of modifications in biology if some one would map out and characterize the areas occupied by the various forms of Cerion in the Bahamas. The differences are quite perceptible, and the conditions under which they arise must be relatively simple. All that has hitherto been done insufficiently exact for the purpose indicated, and the field is a wide one."

 

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