134 PROCEEDINGS OF THE MALACOLOGICAL SOCIETY. 



considerable areas, there has been a rather unnecessary duplication of 

 specific names and consequently much confusion of the literature. 

 The revision of the Nearctic species has not been difficult since 

 cotypes, locotypes, or named specimens (chiefly examined by the late 

 E. W. llopcr) of nearly all have been at hand, but the European 

 species constitute a problem which the writer feels neither the 

 inclination or capability of undertaking ; hence the synonymy of 

 Corneocyclas pulchella, which extends to the Old "World, is another 

 story. It is probable that when the Palaearctic forms are thoroughly 

 worked up they will be found to be comparatively few in number, as 

 is true of the North American species. One of the chief stumbling- 

 blocks in classification seems to be the colour of the epidermis. Since 

 this is known to be not of hereditary consequence, and the grouping 

 of the species offers no particular difficulties, the elucidation of the 

 specific synonymy becomes a comparatively simple problem. 



Genus Corneocyclas, Ferussac.^ 



Tellina (sp.), Gmelin, 1788 {T. piisilla, Ginel.) ; Cijclas (sp.), Say, 

 1817 ( C. duhia, Say = T. Virginica, Gmel.); Corneocyclas (pars), 

 Eerussac, 1818 {T. pusilla, Gmel.); Phi/mesoda, Kafinesque, 1820 

 (C. duhia, Say = ll Virginica, Gmel.); Galdeja, Costa, 1839 

 ( G. tenebrosa, Costa = Pisidium pulchelhim, Jenyns) ; Euqlesia, 

 'Leach MS.,' Gray, 1840 {E. Uensloiviana, 'Leach MS.' (not 

 T. Henslowiana, Shepp.) = 2'. piisilla, Gmel.), in synonymy; 

 Euglesa, Leach, 1852 [T. pusilla, Gmel.); Cycladina, Clessin, 

 1871 {T. pus ilia, Gmel.); Cymatocyclas, Dall, 1903 {Pisidium 

 compressuni, Prime). 

 Type, Tellina pusilla, Gmelin. 



Sub-genus Pisidium (Pfeiffer). 



Cardium (sp.), Montagu, 1803 {Tellina amnica, Miill.) ; Pisidium, 

 Pfeiffer, 1821 {P. oUiquum, Pfr. = T. amnica, Miill.); Pera, 

 'Leach MS.,' Gray, 1840 {P. fluviatilis. Leach MS. = T. amnica, 



^ Dall, Trans. Wagn. Inst., iii (4), p. 1460, 1903, has shown that Corneocyclas, 

 originally based on an assemblage of Cyrenoideffi, from which Tellina 

 pusilla, Gmel., was selected as type, in a restricted sense takes priority 

 over the more familiar name of this group, Pisidium of Pfeiffer. Corneo- 

 cyclas has been generally regarded as a synonym of Sphierium, hence 

 there have been objections to the use of the name in this novel connexion. 

 The problem resolves itself into choosing the lesser of two evils. Pisidium 

 cannot be retained as the genus in any event on account of the prior 

 Pliymesocla of Eafinesque. Anyone floundering through the maze of 

 spelling and names in the Monographie in an attempt to determine what 

 Eafinesque really intended to designate his genus and the species described 

 under it (to say nothing of identifying the former except for the citation of 

 Cyclas dubia. Say), would welcome Corneocyclas as a straw to a drowning 

 man. Since Dall appears to be the first writer to establish a type for 

 Ferussac's group, and the one selected was not excluded from consideration, 

 it does not seem necessary to question why this particular species should 

 have been cited. Already Corneocyclas has found a place in the literature 

 of the American and Australian freshwater Cyrenoids, and, if for no other 

 reason, should not be disregarded without good reason. 



