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44 Monograph of the Species of Pisidium. 361 
of the year by myself in a clay-pit near Augusta, Me. in com- 
pany with the P. compressum. 
19. Pistp1um equate Rafinesque. 
Cabinet of C. A. Poulson, Esq. of Philadelphia. 
Physemoda equale Rafinesque. Bivalves of the Ohio, taken from the 
Annal. Génér. des Sci. Phys. 
Dimensions. Long. 0.80; lat. 0.95; diam. 0.53 inches. 
OssERvaTIONs. Owing to there péin no figure attending 
Rafinesque’s description of this shell, and never having seen 
the original specimens, I have not been able to identify it to 
my satisfaction. 
LIST OF THE KNOWN SPECIES OF PISIDIUM, AND THEIR 
SYNONYMY. 
Y abditum t. America, | Proc. Ac. Nat. Sci. 1, 53. 
2 abruptum, |. America, Proc N. S. 1,53, is P. dubium. 
3 Anne ope, E Meli. de l'Allem. 
à asm, . America, | Stimp. N, E. Moll. Cyclas nitida. 
5 ae . America, | Mss. Cyclas altilis 
^ rn, urope, nyns Monog. las amnica. 
6 oon urope, urton’, - Man. ru 2 
, (. America Ee on 088. 
4 retale, urope, : pei d ; 
9 ci , ope, dans Cat. 841. 
10 dt oe ‘ Alder’s Sap l. Cat. 4... C. cinerea. 
i omg . Ameri Bos . H. Proc. iv. 
1; diaphanum,' America, | Pr. A. N. 8.1, 68. C diaphana. 
12 pete (. America iz's L. yt 245. C 
15 Quplicatum, urope, | Pf. Moll. de [equale. 
: equale, . America Radin. Bivalve of the Ohio. Phys. 
2 equilaterale, : Affari. (uma enr 
i masi , | America, | Bost. S Proc. iv. 162. 
“Gt ürope, is P. 
Pe H siesianum, urope Gassies, e "n 1849. 
daear anum, urope, Jenyns, Monog. € por 
J ? urope, Porro p is P. Pfeifferi. 
pees fare urope, Turton's Man. is P. 
18 : | Europe McGilliv. Moll. of Scot. is P. pulch. 
d a ""|N. America, . N- H. Proc. iv. 162. 
urope, Gassies, Cat. 1849. 
