64 THE NAUTILUS. 



tion is also a peruviana which occurs in our western waters of a 

 larger size and more ponderous than any species we know of." 



The reader will note that Lea identified the giganteus as per- 

 uviana. At this time (1829) he regarded all the plicate shells 

 as being one species. He never mentioned giganteus again ! 

 Can it be that this omission arose because of his very evident 

 wish to protect his name of multiplicatus ? 



With the possible exception of peruviana, the giganteus is the 

 earliest name given to the species, as well as the most appro- 

 priate. Following Lea, Simpson placed "giganteus" (Lea) 

 under plicatus. The giganteus of Barnes however can be noth- 

 ing else than heros. No other Naiad attains the dimensions 

 given by him. 



This species has recently been erected into a separate genus 

 by Utterback, whence its proper name is now Megalonaias 

 giganteus Barnes, 1823. 



PLEISTOCENE MOLLUSCA FROM CALLAWAY COUNTY, MISSOURI. 



BY DARLING K. GREGER, COLUMBIA, MISSOURI. 



During the past season, engineers in charge of river improve- 

 ment being carried on near Mokane, Mo., called my attention 

 to two localities where an abundance of fossil or semi-fossil 

 shells were being unearthed, and upon their invitation to con- 

 duct me to the localities, both were examined, and collections 

 made. 



The first place visited was an excavation on the east bank of 

 Middle River, a short distance below the point of its entrance 

 into the gorge of the Missouri. At a depth of twenty-six feet 

 below the level of the flood-plain of the Missouri River, in a 

 black, sticky clay the following species were gathered: 



Polygyra profunda, Succinea ovalis f, 



Polygyra albolabris, Gastrodonta ligera, 



Polygyra thyroides, Helicina occulta, 



Polygyra elevata, Pyramidula solitaria. 



Polygyra clausa, Pyramidula alternata, 



Polygyra appressa, Pyramidula perspectiva, 



