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 wi/iklciji 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 

 walkeri in having flat-sided whorls, walker! 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 VIKIDIS, RAJFINESftUZ, 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 (NAU- 

 TILUS, XXIX, Sept., 1915), Mr. Bryant Walker filed an "in- 

 terference" (NAUTILUS, 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 viridis 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 NAUTILUS, 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. 



