1850.] 119 



December Zd. 

 Dr. Morton, President, in the Chair. 



A communication was read from the Minister of Public Works of 

 France, dated Paris, Sept. 5th, 1850, accompanying a number of Vols. 

 of the "Journal des Mines," and of the Annates des Mines," which 

 had been deficient in the series of that Work in the Library of the 

 Academy ; and also asking in return, certain numbers of the Journal 

 and Proceedings of this Institution. 



A letter was read from Professor Nillson of Sweden, dated Lund, 

 Sept. 30th, 1850, returning acknowledgments for his election as a Cor- 

 respondent ofthex\cademy,and staling his intention to present a copy of 

 his work on the Fauna of Scandinavian Vertebrata ; and also offering 

 to procure for the Academy, Zoological specimens of that country, if 

 desirable. Referred to the Zoological Committee. 



Dr. Leidy read a paper entitled " New genera of Vermes," which, 

 being intended for publication in the Proceedings, was referred to Drs. 

 Zantzinger, B. H. Coates and Hallowell. 



December lOt/i. 

 Vice-President Bridges, in the Chair. 



Dr. Leidy exhibited several molar teeth and fragments of maxillae 

 of a fossil Rhinoceros, from Missouri territory, received from the 

 Smithsonian Institution through Prof. Baird, which indicate a species 

 little more than half the size of the recent R. indicus. He character- 

 ized it under the name of R. occidentalis. 



Dr. Leidy also exhibited drawings, and offered the following remarks 

 on the nettling organs of the Hydra : 



There are three different forms of these organs. The first are of comparatively 

 large size, and are pyriform in shape, measuring about l-1700ths in. in length, 

 by l-2125ths in. in breadth. They are found principally upon the arms, and 

 anterior two thirds of the surface of the body, although they are found upon the 

 posterior third also, but few in number. Colorless and transparent, they contain 

 within them an elongated pyramidal body about l-3400ths in. in length, the apex 

 of which is in contact with, or slightly protrudes from, the projecting extremity 

 of the nettling cell ; the base is divided into four lobes and rests upon a prolate 

 spheroid body which has its other extremity applied to the middle of the concav- 

 ity of a cup-shaped mass of faintly yellowish matter occupying the inferior third 

 or bas-fond of the receptacle. The pyramidal body is described by Corda* as 

 being a calcareous dart capable of protrusion from the cell, but incorrectly, 

 for when it is forced from its receptacle, it divides into four spine-like 

 processes, which project outward nearly at right angles to the extruded mass. 

 The intervals unoccupied, and the bodies just described within the cell are filled 



Nov. Act. Phys. Med. 1836, p. 301. 



