308 Linnean Society. [Nov. 3, 



is preserved (both in its course of retrovolution and after maturity) 

 by a reflection of the ventral disc soraevifhat analogous to the re- 

 flected mantle of the Covv^ry, but bearing no part in the formation of 

 the shell. 



In support of this vievi' and with the view of proving that this 

 distinction is borne out by the physical condition of the shells at 

 different periods of growth, the author takes for examples Cyprcea 

 Tigris and Oliva Utriculus. The Tiger,Cowry in its first stage is of 

 a uniform light chestnut-bay ; the colour then breaks up, as it were, 

 into bands of close-set blotches of a richer hue ; a coating of white 

 is next superposed, and upon that is deposited a series of rather 

 distant zigzag flames ; these are partially concealed by a second layer 

 of white enamel thinner and more delicate than the preceding one, 

 on which a number of dark spots are subsequently deposited ; and a 

 third coating of white enamel, with a new layer of black and brown 

 spots intermingled, characterizes the maturity of the shell. Each 

 period in the life of the Cowry appears therefore to be distinguished 

 by a different design of colouring ; but this is not the case with the 

 Olive, the shell of which exhibits the same appearance at all stages 

 of its growth, and the different layers of its colouring matter must 

 be deposited simultaneously because the organ of calcification ex- 

 tends only to the lip, from which the shell gradually recedes in the 

 progress of its growth. The external coating of Oliva Utriculus 

 is of an obscure milky-blue, and the removal of this layer by means 

 of an acid reveals a dull ashy ground sprinkled with numerous tri- 

 angular opal-like dashes ; in Oliva Brasiliensis the removal of the 

 outer layer exhibits a longitudinally striped pattern, and other va- 

 rieties of design may be found in different species ; but there is no 

 periodical change of colour in the entire shell to mark its advance- 

 ment in growth. 



November 3. 

 R. Brown, Esq., V.P., in the Chair. 

 Arthur Grote, Esq., was elected a Fellow. 



Read a " Description of the Asafoetida plant of Central Asia." 

 By Hugh Falconer, Esq., M.D., F.L.S. &c. &c. 



Dr. Falconer describes the plant which yields the Asafoetida under 

 the following characters : — 



