Dall — Revision of Cyrenacea. 



Family Sphteriidje. 



Genus Sphmrium Scopoli, 1777. Type Tellina cornea Linne\ North 

 Europe. Cyclas Lamarck not Link, Cornea Megerle, Amesoda Rafin- 

 esque, Cycladites Kriiger, Pisum Bourguignat not Megerle, and Corneola 

 Clessin, not Held, are synonymous. 



Subgenus Sphavium s. s. Type S. corneum Linne\ 



Section Cyrenastrum Bourguignat, 1854. Type 8. solidum. Normand. 

 France. 



Section Sphceriastrum Bourguignat, 1854. Type S. rwicola Leach. 

 England. 



Subgenus Musculium Link, 1807. Type Tellina lacustris Muller. 

 Denmark. Calyculina Clessin is synonymous. 



Subgenus Eupera Bourguignat, 1854. Type Pisidium moquiyiiamim 

 Bourg. Brazil. Limosina Clessin is synonymous. 



Genus Corneocyclas Ferussac, 1818, (restricted). Type Tellina ptmlla 

 Gmelin. Germany. 



Subgenus Corneocyclas. 



Section Corneocylas s. s. Type C. pusilla Gmelin. 



Section Phymesoda Rafinesque, 1820. Type Tellina virginica Gmelin. 

 Virginia. 



Section Pisidium C. Pfeiffer, 1821. Type Tellina amnica Muller. 

 Denmark. 



Section Cyclocalyx Dall (nov.). Type Pisidium scholtzii Clessin. Ger- 

 many. The umbones high and constricted below the nepionic shell, 

 otherwise like Corneocyclas s. s. 



Subgenus Cymatocyclas Dall (nov.). Type Pisidium compressum Prime. 

 Cambridge, Mass. Nepionic valves flat, transversely undulated, sharply 

 marked off from the rest of the disk, otherwise as in Corneocyclas. 



Subgenus Tropidocyclas Dall (nov.). Type Pisidium henslowianum 

 Sheppard. England. Nepionic valves with an oblique, elevated, radial 

 keel and distinctly delimited from the rest of the disk. Fossarina Cles- 

 sin, 1873, not Adams, 1863, is synonymous. 



Notes. 



Pera Leach and Euglesa Leach, 1852, are synonymous with Corneo- 

 cyclas s. s. Galileja Costa; Euglesia Leach, 1840; Pisum Gray, 1847, not 

 Megerle, 1811; Cordula Leach; Fluminina Clessin; Cycladina Clessin; 

 and Rivulina Clessin; are not separable from Pisidium s. s., if judged by 

 their types; most of them are based on perfectly worthless characters. 

 The specific determinations of Westerlund in the 'Fauna der Palsearcti- 



