20 THE NAUTILUS. 



PlSIDIUM ABDITUM Var. LACTEUM St. 



Two live specimens and a few single valves taken in Georges 

 River, North Warren, season of 1913. 



PlSIDIUM SPHAERICUM St. 



About twenty specimens, mostly immaculate, a few nearly full 

 grown, taken Aug., 1913, in Georges River, North Warren. 



AMNICOLA SCHROKINGERI Frauenfeldt. 



Collected by Rev. Henry W. Winkley, at Saco, York county. 

 LTMN^EA DESIDIOSA var. PLICA Lea. 



Collected in Buckfield, Oxford County, by John A. Allen. 

 PLANORBIS HIRSUTUS Gld. (= albus Mull) and P. DEFLECTUS Say. 



Were inadvertently omitted from my published list. The former 

 has been reported from Aroostook, Knox and Penobscot counties ; 

 the latter from Aroostook, Knox, Oxford and Penobscot counties. 



VERTIGO NYLANDERI St. 



Woodland, Aroostook Co. (Nylander). See NAUTILUS, Vol. 

 XXII, p. 107. 



STUDIES IN NAJADES. 



BY DR. A. E. ORTMANN. 



(Continued from Vol. XXVll, p. 91.) 



FUSCONAJA ASKEWI (Marsh). (See : Quadrula a. Simpson, 1900, 

 p. 786.) 



A number of specimens, among them males, sterile and gravid 

 females, from Sabine River, Logansport, De Soto Par., Louisiana, 

 were received from D. S. Frierson, mostly collected on August 1, 

 1912, but one gravid female was collected on September 21. 



In all females (altogether eleven) all four gills had marsupial 

 structure, and in five gravid ones all four gills were charged. But in 

 one gravid individual only the outer gills contained glochidia; but 

 the inner gills had distinctly marsupial structure. Since there were 

 placentae and fragments of them in the suprabranchial canals and the 

 cloaca cavity, this specimen was caught in the act of discharging. 



The breeding season probably ends in August, but the gravid spec- 

 J men, with glochidia, collected on September 21, is remarkable. It 



