( 34 ) 



7. Cyclostoma. (1) Lam. 



Oval - spiral , moulh Mouth bordered by a 

 round or nearly round, callous pad. 

 closed entirely by a round, 

 thin, calcareous opercu- 

 lum : peristoma complete. 

 PI. 9, fig. 13, 14. 



8. Valvata. Muller. 



Rolled almost in the 

 same plane. PI. 9, fig. 22. 



( Cricostomata.) 



Terrestrial and aqua- 

 tic. 



V. Animal, p. 66. 



Fresh waters. 

 V. Animal, p. 66. 



9. Paludina. (2) Lam. 

 Vivipara. Montfort. 



Oval -spiral; opercu- Mouth with a small Marine, and in stag- 

 lam with an angle like angle towards the upper nant waters. 

 that of the mouth. PI. 9, part. V. Animal, p. 66. 



fig. 15. 



10. Monodonta. Lam. 



Oval, or conical ; oper- A blunt and slightly 

 culum round, horny. PI. projecting tooth at the 

 9, fig. 25. base of the columella. 



Base flat or concave. 



Marine. 



V. Animal, p. 66. 



(1) Young Cyclostomce may sometimes be confounded with the shell of the genus 

 Turbo; for the upper part of the peristoma is not completed, that is to say, the 

 lips do not join, before the adult state ; in the Turbo they always remain separated. 

 The Misscnau chain of hills near Mayence is composed of fossil Cyclostomse, not of 

 Bulimi, and of two species which, according to M. de Ferussac, are again found in 

 Quercy 9 Agenois, and in Silesia. M. Brongniart expects that the Cyclostoma? will 

 hereafter be divided into two genera ; the one aquatic, the other terrestrial. The 

 C. mumia, Lam. pi. 4, fig. 1, belongs to the latter ; it has only been found as yet 

 in the 1st ox Lower Fresh Water Formation in the environs of Paris ; M. Brongniart 

 conceives that on further investigation it may be found to characterise it: the 

 enlargement or projection of the upper part of the peristoma is uot unfrequent in 

 the living species. All those indicated at Grignon differ from true Cyclostoma?* 

 The Cyclostoma car ina ta of the canals of Egypt, PI. 13, fig. 9; C. bullmoldes of the 

 environs of Alexandria, PI. 8, fig. 13 ; C. unicolor, PI. 8, fig. 15 ; and the Helix cre- 

 nelata, PI. 12, fig. 10 ; brought by Olivier, differ in form from all the other fresh- 

 water shells yet known, and, as M. Brongniart justly observes, if found in the fossil 



tate, would certainly have been considered as marine. 



(2) Foss. in Gravel and Alluvial Clay; London Clay; Crag Marl. 



