266 PROCEEDINGS OF THE ACADEMY OF 



November 5. 

 The President, Dr. Ruschenberger, in the chair. 



Thirty-three members present. 



The following paper was presented for publication : 



" Description of some new genera of Mollusca." By Wm. M. 

 Gabb. 



Mr. Joseph Willcox stated that having felt much interest in 

 the subject of corundum, he had frequently visited the localities 

 of that mineral in Pennsylvania ; and that during last April he 

 visited many corundum localities in Lowns Co. Ga., and in Clay 

 and Macon Counties in North Carolina. Mr. Willcox exhibited 

 a specimen lately obtained from near Unionville, Pa., the central 

 portion of which was corundum surrounded by chlorite. The ex- 

 terior part of the corundum was so mixed with chlorite, that there 

 appeared to be an alteration of one of the substances into the 

 other. Mr. Willcox said he had frequentby found in several locali- 

 ties in North Carolina, round specimens of chlorite, the central 

 portions of which were corundum, which corresponded in shape to 

 the surrounding mass of chlorite. These nodules of corundum 

 were from one-quarter inch in size to three inches. In some of the 

 specimens the lines were well defined between the corundum and 

 chlorite, while in others these two substances were so mixed as to 

 appear to pass into each other b} r insensible degrees. 



Mr. Willcox said he had never seen a specimen of this character 

 from any corundum localitj 7 in Pennsylvania before. Mr. Willcox 

 also exhibited specimens of crystals of corundum from Laurens 

 District in South Carolina ; one of which was partly altered into 

 margarite, and another was wholly converted into the latter sub- 

 stance. 



Mr. Thomas Meehan, referring to the cylindrical production 

 presented by Prof. Leidy, said he thought he could confirm Prof. 

 Leidy's suspicion that it was not of vegetable origin, but' was 

 wholly mineral. There was not only the peculiarity in the appa- 

 rent concentric laj'ers, referred to by Prof. Leidy, but also an 

 entire absence of any trace of medullary rays which he thought 

 never wholly obsolete in woody petrifactions. But beyond this 

 the diameter of what appeared to have been the pith cavity was 

 far bej'ond what usuall} T occurred in Dicotyledonous structures of 

 the age which this, by the number of circles, ought to be. Although 

 lie believed the suggestion had not been made before, he had reason 

 to believe that the pith cavity decreased in diameter with the age 



