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PROCEEDINGS OF THE ACADEMY OF 



The following paper was presented for publication : 

 " Description of six new species of Fresh Water Shells." By 

 Isaac Lea. 



June 22d. 



Dr. Euschenberger, Vice-President, in the Chair. 



Twenty-three members present. 



The death of Dr. Charles D. Meigs was announced. 



The following paper was presented for publication : 



" Notice of certain obscurely known species of American Birds, 



based on specimens in the museum of the Smithsonian Institution." 



By Robt. Ridgway. 



June 29th. 



The President, Dr. Hays, in the Chair. 



Twenty-five members present. 



The report of the Biological and Microscopical Section was 

 presented and referred to the Publication Committee. 



On permission being granted, Mr. Warner spoke upon the mathematical rep- 

 resentation of organic forms. Such limitations, he said, might serre to narrow 

 the field of research into the physical causes of organic forms, and perhaps 

 furnish the suggestion of a rational theory of these causes. If no other ad- 

 vantage were derivable from imitations of this kind, they might, he thought, 

 be useful for description and classification. 



He exhibited a representation of the longitudinal section of ap egg by a 

 curve which he called the hyper-ellipse, and of the section of an embryo by 

 another curve which he termed a deformed lemniscate. Of the egg curve, he said 

 that it very closely resembled an ideal section of an egg taken from a standard 

 modern work. Of the curve representing the embryo he said that it not im- 

 probably marked the boundary of matter lying within it, in a diflfereut state of 

 temperature, density, or tension from the matter lying without. These repre- 

 sentations were verified by the members present. The speaker expressed the 

 intention of making these representations the subject of a future paper, in 

 which he would give drawings and formulae. 



The following gentlemen were elected members : 



Dr. N. R. Bradner, U. S. N. ; Charles B. Nancrede, M. D., and 

 Harry Emlen. 



Alexander Carte, of Dublin, was elected a correspondent. 



On favorable report of the Committees, the following papers were 

 ordered to be published : 



Descriptions of six new species of FRESH WATEE SHELLS. 



BY ISAAC LEA. 



Unio Macnielii. — Testa sulcata, oblonga, valde infequilaterali, antice sub- 

 rotunda, postice obtuse biangulata; valvulis crassiusculis, antice crassioribus; 

 natibus prominulis ; epidermide fusca vel luteola, postice viridi radiata ; den- 



[June, 



