194 



species had been described by Tellkampf, and named Astacus 

 pellucidus. 



Prof. A. mentioned a remarkable fact, ascertained by Erich- 

 son, with regard to the Crawfishes of America. They have all 

 one pair of gills less than those of the old world. 



Dr. Channing also presented to the collection of the Society a 

 large umbel-shaped mass of Fossil Coral, which seemed to con- 

 stitute an entire individual, and which is a specimen of similar 

 masses which occur scattered through the limestone near Sharon 

 Springs, Schoharie county, New York. No attempt was made 

 to name it, or give its special characteristics. 



Dr. C. placed upon the table some of the Seeds of the Wild 

 Oat, with the beard attached, procured by him from the uplands 

 of the prairies in Wisconsin during the past summer. The beards 

 of these were in some instances five inches long, and presented 

 the spiral structure which gives the smaller variety of animated 

 oat its peculiar sensitiveness to moisture. These specimens 

 were picked on the 28th of June, before the seed was quite ma- 

 ture, and, perhaps on this account, seemed to be only slightly 

 influenced by hygrometric changes. The stalk grows about 

 three feet high ; and as the supply is very large, especially in 

 Middle and Northern Wisconsin, it may be worth while to re- 

 member the locality. 



Dr. C. also exhibited some cases of the larvae of trichopterous 

 insects from a pond in the north of New Hampshire. These 

 cases were spoken of as remarkable from their shape, which 

 was an elongated quadrilateral pyramid, presenting right angles 

 and flat sides. The larva exhibits very brilliant colors of black 

 and green. 



Dr. Channing presented a fragment of a leaden conduit 

 from Pompeii. 



He had intended to have made an examination of the change 

 the metal had undergone from the lapse of time, but had not yet 

 done so. He ofliered it to any gentleman who might be disposed 

 to examine it. At the request of Dr. Jackson, he consented to 

 resume it, and pursue the inquiry himself. 



Dr. C. T. Jackson read, from English papers and periodi- 

 cals, notices of Gun cotton, with a view of showing the date 



