THE NAUTILUS. 139 



6364, and in the collection of Mr. Lermond. Also at other places 

 in the vicinity of Warren, Me. 



The shape of the mussel is quite peculiar, especially in front or 

 rear aspect, and if there were only one or a few specimens, they 

 might be regarded as abnormal. Some forms of P. medianum St. 

 are of somewhat similar shape, in lateral view, but they are of light 

 color, the shell is not transparent, the surface dullisli, and the hinge 

 is quite different. Young and half-grown specimens may be mistaken 

 for P. splendidulum. 



Sphaerium acuminatum (Pme.), Oyclas acuminata Prime, Proc. 

 Boston Soc. Nat. Hist., iv, p. 155, 1851, was made a synonym of «S. 

 striatinum (Lam.) in Mon. Corb., p. 37, by Prime, but it is dis- 

 tinct, as evidenced by the specimens (a few valves) in the Prime 

 collection.* 



Cyclas alhula Pme., 1. c, is probably the same, to judge from the 

 specimens — two poor, washed left valves in the Boston Society Nat- 

 ural History (No. 8086) — but not from the description. There are 

 no specimens of C. albida in the Prime collection (Mus. Comp. Zool.). 

 and for the above reasons it r.ppears proper to use the name acumi- 

 nata, though alhula has precedence, yet both are on the same page. 



The species is common in the great-lake region, and rather 

 variable. 



S. okioense n. sp Mussel somewhat inequipartite and elongate, 



moderately inflated, the valves rather flat toward the margins, 

 superior and inferior margins slightly curved, anterior margin 

 rounded or obliquely subtruncate above, posterior obliquely truncate 

 to subtruncate, end rounded ; beaks small, slightly elevated ; scutum 

 and scutellum rather long, narrow ; surface dull, with rather fine 

 striae — or sulci ; color straw to yellowish corneous to grayish in old 

 specimens ; shell rather thin, hinge slight, plate narrow ; cardinal 

 teeth small, short, posterior part of the right thick, nearly cubical, 

 laminae slight ; ligament and resilium rather long, slight. 



Long. 11.5, alt. 8.2, diaro. 5.3 (100: 73: 45). 



Soft parts not examined. 



Hab.; Ohio River and tributary. At Cincinnati on Nov. 1, 1895, 

 I collected a good number of specimens, young to adult, in com- 



1 " Origin," probably from Lake Superior, also two valves in the Boston So- 

 ciety of Natural History (No. 8086). 



