﻿HAMUSINA. 



305 



Nevertheless the more salient features of the British arid Sicilian shells 

 approximate sufficiently to justify our regarding the two forms as varieties of one 

 species. 



Our best specimens occur in the Murchisonae-zone of Babylon Hill. Hence we 

 might name this form H. Damesi, var. Babylonica. It is also found sparingly on the 

 same horizon at Stoford and Bradford Abbas. Modifications of ornament induced 

 by solvents are apt sometimes to produce rather puzzling results in this species. 



239. Hamusina Oppelensls, Lycett, 1857. Plate XXIV, fig. 13 (Coker variety), 



fig. 14 (type refigured). 



1S57. Tcrbo Oppelensis, Lycett. The Cotteswold Hills, p. 127, pi. iii, fig. S. 

 Cf. also Turbo Bektheloti, iVOrbujny. Prodrome, i, p. 24S ; and Terr. Jur., vol. ii, 



p. 337, pi. ccexxviii, figs. 7 and 8. 



Bibliography, Sfc. — Lycett observes that this is a remarkable species, resembling 

 Turbo Bertheloti in its general figure and sinistral spire, but the latter has a 

 double row of tubercles, and is destitute of the transverse ribs. As the result of 

 a careful examination of the only three available specimens from the Cotteswolds, 

 I am forced to conclude that the strong transverse (axial) ribs shown in the 

 original figure, and also in PI. XXIV, fig. 14, of the present work, are not structural 

 features. The real ornamentation is more truly depicted in the large shell from 

 Coker (fig. 13) ; but the Cotteswold specimens show it more or less, though the 

 ornaments have been variously modified by mineralisation and development from 

 a hard and unkindly matrix. As so often the case, the " type " is an unfortunate 

 specimen, calculated to mislead alike the author, the artist, and the reader. 



The subjoined description of Hamusina Oppelensis is based partly on Cotteswold 

 and partly on Coker specimens. It would seem to be a very general rule that 

 species of Gasteropoda, as they are followed from Dorset-Somerset into the 

 Cotteswolds, diminish greatly in size. The sinistral Gasteropods are no exception 

 to the rule. 



Description : 



Length .... 30 — 50 mm. 



Height of body- whorl to total length . 35 to 40 : 100. 



Spiral angle about . . . 46°. 



Shell sinistral, thin, conical, without umbilicus. Apical conditions unknown. 

 Number of whorls about eight ; these are somewhat convex towards the centre, 

 and upon the convexity is a single row of tubercles ; at the anterior extremity is 



39 



