COLLECTION OF SHELLS. 



when met with in the fossil state, they prove the 

 str ata to beof fresh water formation. 



1 3th. The animals composing the numerous 

 family helicoidea are very noxious on cultivated 

 ground. The species most esteemed by concho- 

 logists belong to the genera bulimus, achatina^ 

 and auricula. We have one hundred and ninety- 

 two species of helices ; these are terrestrial shells 

 from all countries, the most curious of which 

 is the h. vesicalis. 



Our knowledge of the next order, gasteropoda^ 

 is due to the anatomical labours of M. Cuvier, 

 and from his observations M. de Lamarck has di- 

 divided it into families. The greater number of 

 the animals which compose it are destitute of 

 a shell ; we shall notice only those which are 

 provided with one. The Umax arid other genera 

 which have no shell are preserved in spirits of 

 wine among the naked mollusca. 



The family of the bullcecK is very numerous , bu t 

 owing to the lightness and fragility of their shell, 

 they are rare in collections ; on this account that 

 of the Museum which has twenty-four species is 

 valuable to the student. 



The family calyptrece is composed of eight ge- 

 nera: the crepidulce to the number of fourteen 

 species, and the calyptn&ce to that of twenty, are 

 distinguished by the interior partition of their 



53, 



