THE NAUTILUS. 127 
Length, 12.0; width, 6.0. Lea’s specimen. 
This Physa is related to Physa anatina which is so common 
in the States west of the Mississippi River. The occurrence of 
this species so far east of its usually recorded range (it is said 
by Walker to extend clear across southern Michigan, however) 
is as surprising as is the presence of the race of the New Eng- 
land Amnicola winkleyi. It was at first thought to be a recog- 
nizable race of anatina but the presence of narrow individuals 
indicates its relation to Lea’s species. It differs from Physa 
walkert in having flat-sided whorls, walkeri having rounded 
whorls and deeply impressed sutures. Many of the Pleistocene 
mollusca differ somewhat from their living representatives but 
in most cases this difference is not enough to cause their sep- 
aration as new species or varieties. Among the Physas, also, 
the range of variation in the different species is known for but 
a few species; when this important characteristic is more gener- 
ally known it will be safer to describe new species in this poly- 
morphic genus. 
LASMIGONA VIRIDIS, RAFINESQUE, 1820. 
BY L. G. FRIERSON. 
The adoption of the above as the correct specific name of the 
old Unio pressus Lea having been urged by the writer (Nav- 
TILUs, X XIX, Sept., 1915), Mr. Bryant Walker filed an ‘‘ in- 
terference’’ (Nautitus, XXIX, Nov., 1915) for the purpose 
he stated ‘‘ of suspending the general adoption of the proposed change 
until such time as certain important and probably conclusive facts can 
be obtained.’’ 
As the current year will round out a century since Rafinesque 
published his virdis the acquisition of any new facts concern- 
ing the case would seem rather remote; and as silence might be 
construed as consent, and the proposed ‘‘suspension’’ become 
permanent, the writer, with the consent of Nauriius, makes 
bold to again appear in court. 
Rafinesque ascribed to his species the following characters: 
Shell inequilateral, elliptical, obliquely truncate posteriorly. 
A little convex; hardly thick. 
