SYNOPSIS OF THE NAIADES— SIMPSON. 743 



* t UNIO OBESUS var. PALUDICOLUS Gould. 



*Unio paludicolus Gould, Pr. Bost. Soc. Nat. Hist., II, 18-15, p. 53. — * Gould, 

 Otia. Couch., 1852, p. 197.— * H. and A. Adams, Gen. Eec. Moll., II, 1857, 

 p. 493.— '' B. H. Wright, Check List, 1888. 



* Margaron (Unio) paludicolus Lea, Syn., 1852, p. 33; 1870, p. 54. 



* Unio pahidicolor Conrad, Pr. Ac. N. Sci. Phila., VI, 1853, p. 254. — * P^etel, Conch. 



Sam., Ill, 1890, p. 162. 



Southern Virginia southward in streams draining into the Atlantic, 

 and throughout the peninsula of Florida. 



tUNIO BISSELLIANUS Lea. 



* Unio bisaellianus Lea, Pr. Ac. N. Sci. Phila., XI, 1867, p. 81; * Jl. Ac. N. Sci. 



Phila., VI, 1868, p. 277, pi. xxxvii, fig. 90; * Obs., XII, 1869, p. 37, pi. 

 XXXVII, fig. 90. — * B. H. Wright, Check List, 1888. — * P^tel, Conch. 8am., 

 Ill, 1890, p. 146. 



* Margaron (Unio) hissellianus Lea, Syn., 1890, p. 50. 



Bissell's Pond, Charlotte, I^orth Carolina. 



tUNIO SUBLURIDUS Simpson. 



* Unio suhhiridus Simpson, Pr. U. S. Nat. Mus., XV, 1892, p. 432, pi. lxxiii, figs. 



3,4. 



Orange Springs, Marion County, Florida. I can not be certain as to 

 the relationship of this species, as the beaks are eroded in the only 

 shells I have seen. 



Section MIGRONAIAS Simpson, 1900, 

 (Type, Unio aratus Lea.) 



Shell small, oval, a little produced near the posterior base, with a 

 moderate posterior ridge and pointed near the base behind; beaks 

 rather prominent, the sculpture beiiDg apparently rather line, irregu- 

 larly concentric ridges, having a tendency to fall into two loops; the 

 whole surface strongly and closely concentrically ridged; i)seudocardi- 

 nals compressed, high, slightly curved upward; laterals compressed, 

 curved ; beak cavities moderately deep ; nacre whitish ; anterior muscle 

 scars deep, rough ; posterior well marked. 



Animal with the marsupium pad-like, occupying all but the extreme 

 posterior part of the outer gills ; branchia? elongated, wider behind, inner 

 the larger throughout, free from the abdominal sac or united to it;' 

 palpi large, rounded behind; mantle with thickened border; anal 

 opening crenulate. 



' In some specimens free throughout; in others entirely united. 



