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GASTEROPODA OF THE INFERIOR OOLITE. 



245. Cirrus Calisto, d'Orbigny, 1850. Plate XXV, fig. 1 (British variety). 



1850. Turbo Calisto, d'Orbigny. Prodrome, vol. i, p. 300. 



1852. — — — Terr. Jur., ii, p. 345, pi. cccxxxii, figs. 9, 10. 



1879. Cirrus Calisto, d'Orbigny, sp., J. Buckman. Proc. Dorset N. H. Field 



Club, p. 139, pi., figs. 6, 6 a. 

 1884. Hamusina Calisto, d'Orbigny, sp., Cossmann. Et. Bath., p. 249, pi. xiv, 



fig. 5. 



Bibliography, fyc. — Rather than make a new species on this occasion I prefer 

 to follow the example of J. Buckman, and identify the Coker fossils with 

 d'Orbigny's species. There are certain difficulties which present themselves with 

 respect to " Turbo " Calisto. The type required some restoration, and thus it 

 came to pass that d'Orbigny and Cossmann have differed somewhat as to the 

 interpretation to be placed upon the fragments at their disposal. Moreover the 

 French specimen is said to come from the Bathonian of Luc, whereas it is 

 important to remember that no species of Cirrus or of Hamusina is known from 

 the Great Oolite of this country, nor even from the Upper Division of the 

 Inferior Oolite. 



D'Orbigny's original diagnosis in the ' Prodrome ' fits our specimens very well : 

 " Magnificent sinistral species, whose convex whorls are striated spirally [en long~\ 

 and ornamented with thick transverse undulations near the suture." The Calisto- 

 group includes Cirrus pyramidalis and Cirrus varicosus, and appears to be 

 connected with the Leach /'-group through var. d of the latter species and its 

 modifications. 



Description : 



Length . . . • .50 mm. 



Height of body- whorl to total length . . 42 : 100. 



Spiral angle .... 60°. 



Shell sinistral, turbinate, umbilicated ; apical conditions unknown. The 

 number of whorls is conjectural, but the indications point to about ten, as there 

 is every probability that the spire contracts with a concave spiral angle. The 

 sutures of the lower whorls are wide, almost to gaping. The umbilicus is funnel- 

 shaped, and of moderate width. There is no need to add further to d'Orbigny's 

 description. 



Relations and Distribution. — The differences which separate this species from 

 Cirrus pyramidalis are little more than varietal, such differences being accentuated 

 by change of matrix. What I have termed the British variety of Cirrus Calisto is 

 not very uncommon at Coker, though generally much smaller than the figured 

 specimen. These specimens bear considerable resemblance to each other, so that 



