NATURAL SCIENCES OF PHILADELPHIA. 145 



noted bj' Prof. Clark, and confirmed by Mr Carter. The spongo- 

 zoon is a globular cell, surmounted by a delicate cup, from the 

 bottom of whicli projects a tlagellum. The little animals are situ- 

 ated on the interior of hollow si:)heres of the sponges sustained 

 b}' the skeleton of the compressed animal, whether this be corne- 

 ous, as in the common sponge, or whether it be siliceous or calca- 

 reous. The observations of Prof. Clark had been made on a fresh 

 water sponge, to which he had given the name of Spongilla arach- 

 noidea. Mr. Carter's observations had been made on both fresh- 

 water sponges and the difterent classes of marine sponges. Prof. 

 Leidy at first supposed that the sponge described by Prof. Clark 

 might be the one he had formerly noticed under the name of Spon- 

 gilla fragiliH (Proc. A. N. S. 1851, 278), but comparison proved 

 them to be different. They are both of the same color, but the 

 siliceous spicules of S. arachnoidea are stated to be tuberculate, 

 while they are smooth in S. fragilis. Dr. Leidy had examined the 

 spongozoon of the latter, and found that it presented the same 

 essential structure as described b}' Prof. Clark and Mr. Carter in 

 other sponges. 



Prof. Leidy further remarked that he had found several speci- 

 mens of the curious rhizopod, discovered by Cienkowski, and 

 named by him Clathrulina elegans. They were found among Utri- 

 cularia, but though retaining their stems were unattached and 

 apparently dead. One of the specimens presented a peculiar and 

 as 3-et unexplained character. On one side of the laticed head 

 the orifices were capped with little inverted, hemispherical cups, 

 from the top of which projected a funnel like the cup of the spon- 

 gozoa. Prof. Leid}^ was pursuing his searcli for the living and 

 attached Clathrulina. 



Prof. Leeds made some remarks concerning a remarkable mine- 

 ral found in a bank of white sand near Fa^'etteville, N. C. It was, 

 in appearance, a rod of glass, four feet in length and two inches 

 in diameter, which was made up of a great number of irregular 

 fragments. These fragments were iiighly polished on one side 

 the side apparentl3' turned toward the hollow axis of the rod, and 

 excessively contorted on the exterior side. They consisted almost 

 entirely of silex, the remainder being cliieflj^ oxide of iron. Ac- 

 curate analj'sis showed that the percentages of the constituents 

 in these siliceous fragments and in the sand found in the hollow 

 core of the rod were the same. On account of this identit}'^ in 

 composition, and the incompetency^ of anj^ other known agent to 

 produce such a fusion of almost pure silex, it was concluded that 

 this "rod of glass" was a result of lightning a lightning-lube or 

 fulgurite^ as such products have been called. 



Prof. Leeds also gave the particulars concerning a great eleva- 

 tion of temperature which had occurred in the adit level of a lead 

 mine in Missouri, where the heat had suddenly risen from 60 to 



