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GASTEROPODA OF THE INFERIOR OOLITE. 



ber of whorls about twelve ; the earliest recognisable are flat without turriting, 

 and ornamented by spirals decussating with numerous axial ribs, the most pro- 

 minent spiral being a little below the centre (see enlargement of fig. 17). Pre- 

 sently the whorls of the spire are seen to be turrited in steps with a central keel, 

 which is very salient and nodose, and a less conspicuous anterior keel, which forms 

 a thin serrated border. In the matured whorls the strong axial ribbing of the 

 earlier portions of the spire has a tendency to become faint ; the growth-lines 

 are numerous and fine. 



The body-whorl is angular, subventricose, and bicarinate, but the lower keel 

 representing the serrated border is apparently not salient or much tuberculated. 

 The character of the base is not established with certainty (the specimen, fig. 17, 

 is defective in this respect), but it is probably more or less marked by axial 

 ribbing ; umbilicus funnel-shaped and deep. Aperture circular, small, and 

 adherent. 



Relations and Distribution. — This elegant and conical species is a member of the 

 Leachi-growp, and there are so many intermediate forms {? Cirrus intermedins, 

 J. Buckman) that one cannot doubt the one passes into the other. It is distin- 

 guished from the majority of specimens of Cirrus Leachi by a greater number of 

 whorls, by its more conical figure, by the less concavity of the spiral angle, and 

 the less ventricose figure of the body-whorl. On the whole, likewise, the 

 ornamentation is less rugose, and the axial ribbing of the spire whorls less 

 strongly developed, whilst the whorls themselves are more disposed in steps. 



Occurs sparingly in the Murchdso7ise-zone of Coker and Stoford. 



As regards Cirrus intermedins, Buckm., if this really is the immature form of 

 C. gradatus, then the older name would take precedence. But there seems to be 

 so much doubt as to what Cirrus intermedins really is that I prefer to keep them 

 distinct for the present. 



243. Cirrus Leachi, Sowerby, 1818. Plate XXV, figs. 3, 4, and 5. 



1818. Cirrus Leachi, Sow. Min. Couch., pi. ccxix, fig. 3, and r fig. 1. 



18GG. — (T. Hornesi or T. Bertheloti), Moore. Middle and Upper Lias 



N.W. England, p. 94, pi. vi, 

 figs. 7, 8. 



isTO. Leachi, Sow.; sp., J. Buckman. Proc. Dorset N. H. Field Club, 



vol. iii, p. 137, pi., figs. 1 and 2. 

 Cf. for doubtful members of the Leach /-group — 

 1816. Cirrus nodosus, Sow. (No. 1) — Min. Couch., pi. cxli, fig. 2. 

 1879. — intermedius, /. Buckman. Op. et vol. cit., p. 138, pi. , figs. 4, 4 a. 



