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GASTEROPODA OF THE INFERIOR OOLITE. 



Amberleya, though its affinities may possibly be stronger with Liassic forms of 

 that genus than my own experience enables me to recognise. Certainly one 

 would say that the Oolitic Amberleyas differ widely both from Hamusina and 

 from Cirrus, more especially in the character of the aperture. The most marked 

 difference between Amberleya, as developed in the Inferior Oolite, and Hamusina 

 is the shortness of the columellar area in Hamusina, a feature which it shares 

 with Cirrus. The probable relations of Hamusina will be more conveniently 

 discussed when we consider the possible position of Cirrus itself. 



238. Hamusina Damesi, Gemmellaro, 1878, var. "Babylonica." Plate XXIV, fig. 12. 



1878. Hamusina Damesi, Gemmellaro. Faune Giuresi, &c, p. 338, pi. xxvi, figs. 



39—41. 



Description (British variety) : 



Length . . . . .35 mm. 



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



Spiral angle .... 40°. 



Shell sinistral, thin, conical, turrited, without umbilicus. Spire acute, 

 consisting of seven or eight whorls, keeled towards the base, and slightly 

 hollowed out towards the centre. The ornaments are somewhat rugose ; close 

 to the posterior margin in each of the more adult whorls is a zone of tubercula- 

 tions ; below this are some fine undulating spirals, their number increasing with 

 each successive whorl ; a little above the dominant keel is another zone of 

 tuberculations, each tubercle being connected with a corresponding one in the 

 posterior zone by a rugose axial rib sloping from right to left ; these ribs are less 

 strong in the penult, and are almost effete in the body -whorl ; growth-lines, 

 sloping from right to left, pervade the entire shell. 



The body-whorl is angular, with a flattish base, becoming subconvex towards 

 the aperture ; the ornamentation is substantially as in the spire- whorls, but the 

 fine, undulating spiral lines are more numerous ; these decussate with axial 

 stride. So likewise in the base. The aperture is rounded on the columellar 

 side, the columella being extremely short and incrusted, but the outer lip is 

 angular, and drawn out laterally. 



Relations and Distribution. — The details of ornamentation differ considerably 

 from Gemmellaro's type, the principal difference being that in the English specimens 

 the keel is more anterior. The smoothness of the base in Gemmellaro's specimen 

 was most probably due to the accidents of conservation, since it is not probable 

 that a shell whose sides are so rugose should possess a perfectly smooth base. 



