28 Calvin Goodrich 



the basal margin usually so. The nucleus is small, pit like. The number 

 •of whorls is probably three. Such spiral lines as can be made out under 

 the glass become lost in the material of the operculum after about one and 

 •one-quarter whorls. 



Measurements of shells: 



All are from Weduska Shoals. 



Anculosa coosaensis Lea 

 Fig- 13 

 Anculosa coosaensis Lea, Proc. Nat. Acad. Sci., Phila., March, 1861, p. 54. 



This species, in Tryon's opinion, was the half-grown form of ^l. taeniata 

 Conrad. Specimens of coosaens'is in the Alabama collection show all the 

 marks of maturity in the matter of shell deposit. The animal abandons 

 its spire and confines its life to the body whorl, as in the mature of 

 other fonns. The shell experiences proportionally the same erosion. Tryon's 

 decision, it may be, came about from the fact that certain specimens of 

 taeniata taken by Dr. Schowalter in the Alabama River at Selma are so 

 dwarfed as superficially to resemble Lea's species. A larger series of 

 the true coosaensis than Tryon had before him would, in all likelihood, 

 have prevented this mistake. 



The species is apparently one of the most narrowly confined of the An- 

 culosae. The explorations of Mr. Smith brought it to light only on the 

 Fort William and the Peckerwood shoals of the Coosa River, the second 

 group of shoals being not much more than an extension of the first. Be- 

 cause of this perhaps the variation in form is not great. Ordinarily the 

 body whorl is flattened, but it is sometimes slightly constricted. Spec- 

 imens occur which are subangulated, though typically the periphery is 

 rounded. Numbers of the young are subglobose rather than conic. 



Sculpture consists of fine to rough growth lines, crossed by striae 

 which are sometimes but not always continuous, waving to straight. At 

 times these revolving lines are more nearly to be described as raised 

 than incised. A few shells were found with folds, also a few with sharp 

 carinae as in the young of A. praerosa Say. The plicae when they appear 

 are never more than flat, broad nodules with spots of dark coloring matter 

 between them which brings them into prominence. 



Color varies from yellow to dark brown, a few shells being reddish, a 

 few green. Young shells are more apt to be greenish than older ones. The 

 banding formula is usually four equidistant lines of color, continuous or 

 broken. Of the eight arrangements of banding noted, seven were simple 

 modifications of the prevailing system. Ninety-five shells in a Fort 

 William Shoals lot were banded in epidermis and aperture, 6 in the epider- 



