334 



PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Jail. 31, 



Fig. 1. 



Neritoma sinuosa. 



Nerita, Sow. 1821, Min. Con. t. 217. f. 2. 



Nerita angulata, Sow. 1836, Geol. Trans, vol. iv. t. 23. f. 2. 



Testa ventricosa, sublaevi, fuscescente, spira abbrcTiata,, obtusa, an- 



fractibus quatuor convexiusculis, ultimo obtuse carinato, superne 



depresso, apertura oblonga. 



A rather thick and ventricose shell \nth a slightly elevated and 

 obtuse spire, the last volution carinated about the middle, the carina 

 terminating in the shallow sinus at the edge of the outer lip. The 

 surface is nearly smooth, although in some specimens the lines of 

 growth are well-defined, and become more prominent as the shell 

 approaches the adult state. 



This species was first noticed by Mr. Sowerby, sen., as Nerita 

 sinuosa in the ' jNIineral Conchology,' where its peculiar characters 

 are carefully described, from a specimen collected by Miss Benett at 

 Chilmarsh, near Tisbury, Wilts. 



A cast of this species was subsequently described by Mr. J. D. C. 

 Sowerby, in Dr. Fitton's Memoir*, under the name of Nerita an- 

 giilata, from specimens obtained at Swindon, Wilts, where in the 

 state of casts this species is generally very abundant. 



Locality, Swindon, and near Tisbur}'^, Wilts, in the Portland oolite. 



Neritoma bisinuata. 



Nerita, Buvignier, Statistique Mineralogique et Geologique du 

 Departement des Ardennes, p. 535. t. 5. fig. 12, 13. 



Testci globosa, subleevi, spira depressa, obtusji, ultimo anfractu 

 carinato, ad suturam canaliculato, apertura ovali vel semicirculari. 



A ventricose shell with somewhat angular volutions, marked by 

 the lines of growth, and a depressed spire. The last whorl has a 

 slight furrow at the suture. The aperture is nearly semicircular ; 

 the sinus at the edge of the aperture, corresponding to the carina, is 

 narrow and deep in the adult stage, and only faintly marked in the 

 young shell. J\I. Buvignier in the description of this species remarks. 



* " Observations on some of the strata between the Chalk and Oxford Oolite," 

 Geol. Trans, vol. iv. p. 347. 



