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CATALOGUE 



OF 



SPECIES OF PISID1UM. 



I. THE GENUS PISIDIUM. 



The genus was established in 1821 by C. Pfeiffer (134), who 

 separated it from Cyclas (i. e. SpJuxrium) on good anatomical 

 grounds, namely, as he puts it, that there is a siiujle siphonal tube 

 at the anterior end of the shell. He was obviously unprepared to 

 find in this genus the departure from the normal state of the 

 peleeypod shell whereby the posterior portion is the shorter. 



Prior to Pfeiffer's time forms now referred to his genus were 

 placed in Tellina, by Miiiler and others following him, in Spkcerium, 

 by Scopoli, in Cardiam, by Poli, and in Cyclas, by Draparnaud, 

 Lamarck and his school. 



In 1818 Ferussac, the elder, in an article on "Cyclade" (61), 

 subdivided the genus Cyclas and proposed for one of the sections 

 thus formed the subgeneric name of Corneocyclas, which he stated 

 was equivalent to the genus Cornea of Megerle (t=Sphcerium) (112), 

 bat among the species he cited, following the practice of Draparnaud, 

 were Cychis fontinalis, Drap., C. d tibia, Say, and " C. amnia, 

 tellina amnia, Miill." Corneocyclas does not appear to have been 

 adopted by his cotemporaries, nor does Be Blainville allude to it 

 in his "Manuel de Malaeologie " (1825-27); he merely gives as 

 subdivisions of Cyclas: Cornea and Pisum, Megerle. 



Dr. Dall (49) has recently sought to revive the name Corneo- 

 cyclas for Pisidium on the ground that if one removes all the 

 species included in that subgeuus by Ferussac but now referred to 

 the prior Sphagrium, some species remain that ought to retain the 

 name Corneocyclas. Seeing, however, that the name was only a 

 subgeneric or sectional one, established openly as a synonym for a 

 prior one (Cornea), and that it was never adopted by others, whilst 



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