NATURAL SCIENCES OF PHILADELPHIA. 95 



while in Mexico, United States and Canada, where so many species have been 

 described, there has not been a single one observed. These observations and 

 the followincr list will, I hope, induce more attention to the investigation, by 

 students of Fresh-water Molluscs, of this interesting branch of inquiry. 



List of inequivalve Unionidx. 

 Triquetra contorta, China. Unio encarpus. Central America. 



Spatha Nataleiisis. Africa. Unio Nicaraguensis, Central America. 



Unio tortuosus, China. Anodonta ina^quivalva. Cent. Amer. 



Unio Newcombianus, Cent. America. Anodonta Granadensis, Cent. Amer. 

 Unio Gabbianus, Central America. Anodonta leuticularis. Cent. Amer. 



Unio Nicaraguensis. — Testa sulcata, trjanguliiri, comprcssa. alkjuanto inse- 

 quivalva, inaquilaterali, postice obtuse angulata, anlice oblique truncata ; 

 valvulis crassiusculis ; natibus promLnentibus, subatlutis; ei)icH>nnide olivacea, 

 crebris sulcatis indutis, eradiata ; dentibus cardinalibus erectis, compressis, 

 crenulatis et in valvulo dextro tripartitibus; lateralibus brevious fonicatisque ; 

 margarita argentea et iridescente. 



Habitat. — Lake Nicaragua, Central America. Mr W. M. Gabb. 



Unio Granadensis. — Testa sulcata, elliptica, subinflata, iniequilaterali, pos- 

 tice subangulari, antice rotundata ; valvulis crassiusculis, antice crassioribus ; 

 natibus subprominentibus ; epidermide tenebroso-fusca, nigricanti, eradiata ; 

 dentibus cardinalibus parviusculis, compressis, erectis crenulatisque ; marga- 

 rita alba et iridescente. 



Hab. — Lake Nicaragua, Cent. Amer. Col. E. Jewett and Mr. W. M. Gabb. 



Unio encarpus. — Testa sulcata, subtriangulari, subinflata, aliquanto jnfpjui- 

 valva, inasquilaterali, postice obtuse angulata, antice rotundata; valvulis sub- 

 crassis, antice crassioribus ; natibus prominentibus ; epidermide tenebroso- 

 olivacea, encarpiformi, eradiata; dentibus cardinalibus compressis, erectis, 

 crenulatis, in valvulo dextro subtripartitibus ; lateralibus obliquis rectisque ; 

 margarita albida et iridescente. 



Hub. — Lake Nicaragua. Mr. W. M. Gabb. 



Unio Gabbianus — Testa sulcata, triangulata, subinflata, aliquanto imequi- 

 valva, ina^quilaterali, postice triangulari, anlice oblique truncata ; valvulis 

 crassiusculis, antice aliquanto crassioribus ; natibus prominentibus, ad apices 

 retusis ; epidermide tenebroso-olivacea, obsolete radiata ; dentibus cardinali- 

 bus erectis, compressis et valde crenulatis ; lateralibus curtis, obliquis striatis- 

 que ; margarita argentea et iridescente. 



Hab. — Lake Nicaragua, Cent. Amer. Col. E. Jewett and Mr. W. M. Gabb. 



Anodonta Buidgesii. — Testa Itevi, oblonga, inflata, iniequilaterali, antice et 

 postice rotundata; valvulis pertenuibus : natibus prominulis ; epidermide 

 laevissima, micanti, olivacea, obsolete radiata ; margarita elegantissime iri- 

 descente. 



Hab. — Lake Nicaragua, Cent. Amer. Mr. Thomas Bridges. 



Anodonta in.equivalva. — Testa Isevi, obovata, compressa, inpequivnh-a, in- 

 ffiquilaterali, antice et postice rotundata; valvulis subtenuibus; natibus sub- 

 prominentibus ; epidermide vel luteo-viridi vel tenebroso-viridi, obsolete ra- 

 diata ; margarita c:eruleo-alba et valde iridescente. 



Hab. — Lake Nicaragua, Cent. Amer. Mr. W. M. Gabb. 



Anodonta Jewettiana. — Testa hievi, suboblonga, valde inflata, innequilater- 

 ali, postice rotundata, antice oblique rotundata; valvulis tenuibus ; natibus 

 prominentibus, inflatis ; epidermide olivacea, transverse striata fere sulcata, 

 obsolete radiata ; margarita argentea et valde iridescente. 



Hab. — Lake Nicaragua, Cent. Amer. Col. E. Jewett. 



Anodonta lbnticularis. — Testa Levi, subrotunda, compressa, inxqaicalva^ 

 1868.] 



