CONTENTS 



OF 



VOLUME II. PARTI. 



Officers of the Academy of Natural Sciences, for the 



year 1821. . . . Page 1 



Description of a new Genus; and several new species of 



fresh water Fish, indigenous to the United States. 



By C. A. Le Sueur. . ... 2 



Descriptions of two new species of Exocetus. By C. 



A- Le Sueur. 8 



Descriptions of the Thysanourae of the United States. 



By Thomas Say. ... . . 11 



Observations on the Geological Structure of the Valley of 



the Mississippi. By Thomas Nuttall. . 14 



Notice concerning a new species of American Spider, 



whose web is used in medicine. By N. M.. Hentz. *G& 

 Descriptions of some new Crystalline forms of Phosphate 



of Lime and Zircon. By Dr. G. Troost. . 55 



Descriptions of the Arachnides of the United States. By 



Thomas Say. . . , . 59 



Analysis of the Blue Iron Earth of New Jersey. By 



Lardner Vanuxem. . . 82 



Descriptions of several new species of Cuttle-fish. By C. 



A. Le Sueur. .... 86 



Descriptions of the Myriapodse of the United States. 



By Thomas Say. . . .102 



Descriptions of some new species of Plants recently intro- 



