1856.] 



79 



penera and species of Fossil Fishes from the Carboniferous Strata of 

 Ohio." Referred to Drs. Le Conte, Leidy, and Hallowell. 



Mr. Samuel Ashraead,in presenting the very fine collection of Marine 

 Alga5 made by himself during the past winter at Key "West, Florida, 

 stated that he was indebted to Prof. Bailey, of West Point, for his as- 

 sistance in determining a number of the species. 



Vice President Bridges in the Chair. 



The Committees on Mr. Lea's papers, read 1st inst. ; on Dr. Lcidy's 

 paper, read 8th inst.; on Mr. Kennicott's paper, read 15th inst; on a 

 paper by Messrs. Meek and Hayden, read same date ; on Dr. Leidy's 

 papers, of same date; on Mr. Lea's paper, of same date; and on Dr. 

 Newberry's paper, read 22d inst.; severally reported in favor of publi- 

 cation in the Proceedings. 



Description of a New Sub-Genus of Naiades. 

 By Isaac Lea. 



Family NAIADES. 



Sub-genus Plagiodon. 



Testa ?equivalvis, insequilatera, oblique trigona, valde inflata ; dentibus cardi- 

 nalibus crenulatis, compressis, transversis, curtis, in utraque valva duplicis ; 

 dentibus lateralibus nullius ; ligamentum vix extrorsum ; impressio muscularis 

 antica composita. 



This sub-genus is proposed forafluviatile shell, which is nearer to MonocondT/lcea, 

 D'Orbigny, than to Margaritana, Schumacher ; and may be considered properly 

 so interposed as a link to connect them. 



Plagiodon isocardiodes. 



Testa Iffivi. rotnndo-trigona, globosa, ventricosissima, ad lateris planulatis, 

 valde inquilaterali, antice brevissima, umbonibus tuniidis, valvulis subtenuibus ; 

 natibus valde elcvatis, incurvis, terminalis ; epidermide subrugosa, tenebroso- 

 olivacea; dentibus cardinalibus crenulatis, compressis, transversis, curtis, in 

 utraque valva duplicis ; margarita alba et iridescente. 



Hab. Rio Plata. Mr. E. Verreau, Paris. 



Description of a Ncio Species of Triquetra, Klein (Hyria, Lamarck.') 



By Isaac Lea. 



Triquetra lanceolata. 



Testa laevi, transversissimii, subcompressa, lanceolata, valde inequiTaterali? 

 postice acuto-angulata : antice caudiitim producta ; valvulis crassis ; natil)us 

 parvis, prominulis, ad quartam anteriorem partem positis ; epidermide striata, 

 tenebroso-fusca ; dentibus cardinalibus subgrandibus crenulatisque j lateralibus 

 praelongis rectisque ; margarita alba et argentea. 



Hab. China ? Mr. Asa Fitch. 



