1846.] Linneah Society. 30^ 



serves in a note that the jEshna liasstna of Strickland, a Neuropte- 

 rous insect, of which a lower wing has been found in the lias of 

 Stonesfield, belongs (as Mr. Dale has conjectured) to a genus closely- 

 allied to Petalura, which latter has hitherto only been detected living 

 in New Zealand and New Holland. 



June 16. 



The Lord Bishop of Norwich, President, in the Chair. 



John Birkett, jun., Esq., and Thomas Lightfoot, Esq., M.D., were 

 elected Fellows. 



Read a paper " On the calcifying functions of the Cowry and the 

 Olive, two genera of Pectinibranchiate Mollusks." By Lovell Reeve, 

 Esq., A.L.S. &c. &c. 



After referring to the numerous instances of ver)' considerable 

 modifications in the form of shell and mode of calcification which 

 occur among Mollusca, even in genera very nearly related to each 

 other, Mr. Reeve proceeds to describe more particularly the manner 

 in which the calcifying process is performed in the two genera which 

 form the subject of his paper. Each of these genera produces a 

 porcellanous shell of very analogous structure, consisting of a cy- 

 linder of several enlarging whorls, convoluted on a plane nearly ver- 

 tical to the spire, and composed of layers of vitrified enamel of dif- 

 ferent colours and design ; but there is a striking difference in the 

 calcifying organ as regards its structure and its function of secretion. 

 In the CoviTy the office of calcification is performed by a lobate ex- 

 pansion of the mantle from either side of the aperture, sufficiently 

 large to cover the entire shell, and retracted only under the influence 

 of alarm. In the Olive, on the other hand, the mantle is limited to 

 the interior and the aperture of the shell ; and appears to be furled 

 over the edge of the lip, and retained in a state of tension by a cord 

 or filament passing from its posterior extremity into a narrow channel 

 which is excavated round the spire of the shell in place of the suture. 

 The result of this diflference in the condition of the calcifying organ 

 is, that in the Cowry the testaceous secretion is deposited over the 

 whole shell from the outside in successive layers at different inter- 

 vals of time, while in the Olive the layers must be secreted simul- 

 taneously at the lip alone, and the porcellanous surface of the shell 



