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GASTEROPODA OF THE INFERIOR OOLITE. 



Inferior Oolite in this country, and there occurs one species in the Upper Lias of 

 Compton which may be regarded as a variety of Cirrus LeacJii. This form seems 

 to have been the first of the group in the British Jurassics, and its modified 

 descendant, Cirrus Leachi, remained the demoid species of the Inferior Oolite. 

 These would be classed under Scsevola by Gemmellaro. 



Whatever generic names are assigned to these rugose sinistral Gasteropods, 

 as a matter of fact in this country they nearly all occur on one horizon, viz. 

 the Murchisonge-zone, and are, I suspect, pretty closely related to each other. It 

 would not have been difficult, perhaps, to have folded them all under Cirrus had 

 that genus been more fortunately constituted. 



Bibliography of Cirrus. — In October, 1816, Sowerby gave his diagnosis of the 

 genus, laying great stress upon the funnel-shaped umbilicus. " It is a curious 

 genus, and would be considered a Turbo till modern discernment showed the 

 necessity of nicer distinctions ; having no columella, it represents the whorls of 

 some tendrils called Cirri, or a curled lock of hair ; I have therefore named it 

 Cirrus." 



The sinistral character seems to have been lightly regarded by Sowerby. 

 Accordingly ('Min. Conch.,' t. 141) he described, first, a dextral shell from the 

 Carboniferous Limestone of Derbyshire as Cirrus acutus ; this is referred by 

 Morris to Euomphalus. The second figure on the plate is that of a sinistral shell 

 which Sowerby named Cirrus nodosus. This is interesting as being the first of 

 the group to which I am now referring that was ever figured. The specimen was 

 picked up near Yeovil, and evidently came from the Inferior Oolite of Coker, 

 Stoford, or Bradford Abbas. As Sowerby subsequently described a very different 

 set of shells under the title "nodosus" this form has been named Cirrus inter- 

 medins by J. Buckman. 



In December, 1818, Sowerby (' Min. Conch.,' t. 219, figs. 1, 2, and 4) 

 described Cirrus nodosus, No. 2, from specimens obtained at DuDdry. It is more 

 than probable that two distinct species are included in these three figures. A 

 very imperfectly preserved fragment of a sinistral shell (op. cit., t. 219, fig. 3) 

 was described as Cirrus Leach i. 



In September, 1823, Sowerby (op. cit., tt. 428, 429) described four additional 

 species of Cirrus, all dextral shells, and most probably Pleurotomarias, two being 

 from the Chalk. 



Thus we perceive that the Cirrus of Sowerby, regarded as a genus, includes 

 three distinct genera, viz. Cirrus as restricted to certain sinistral forms, 

 Euomphalus, and Pleurotomaria. It was held to extend from the Carboniferous 

 Limestone to the Chalk inclusive. It will be necessary, therefore, in adopting the 

 generic name Cirrus for a group of sinistral shells occurring in the Inferior Oolite 

 to reconstitute and define the genus, and to eliminate as far as possible those 



