293 



Numerous concentric layers and a radiated crystalline structure 

 are frequently visible. The organic matter is usually in small 

 proportion, though often sufficient to preserve the original form 

 and structure when the cai'bonate of lime is removed by acids ; 

 occasionally there is more animal matter than in true pearls. 



It is to be regretted that the origin of the cocoa-nut pearl is not 

 certainly known, since neither the chemical nor microscopic char- 

 acters are sufficient to point out its source and mode of formation. 

 AYere the statement of its origin perfectly reliable, it might be 

 regarded as the product of a diseased condition of the nut. The 

 concentric lamination might seem to require a longer time than 

 the rapid growth of the cocoa-nut would admit of, but in the case 

 of animal calculi of similar chemical composition, and of such as 

 can be made artificially, these layers, whether resulting from suc- 

 cessive depositions or from a process of segregation, may be 

 rapidly formed. A few weeks, and sometimes only a few hours, 

 are sufficient for the production of numerous laminae. 



Prof. Rogers presented, in the name of Mr. Urbino, a 

 work by H. Wagner on cryptogamic botany with her- 

 barium, and a work on Juncacece, Graminece, &c. ; he 

 also presented from R. B. Forbes, Esq., the half of a 

 large geode from Uraguay, consisting of chalcedonic 

 quartz, very flint-like on the outside ; the thanks of the 

 Society were voted for these donations. 



The President observed, in reference to the last speci- 

 men, that such geodes, and agates, are very abundant 

 in that region, but that they are not in place, having 

 been transported by the river from the north. This was 

 obtained at Salto. 



Mr. A. T. Lyman having resigned the curatorship of 

 Conchology, Dr. Gould, Mr. Whittemore, and Dr. White 

 were chosen a Committee to nominate a candidate for 

 the office. 



The President gave an account of some dissections 

 which he had recently made of the poison apparatus of 

 the rattlesnake. * 



