6 Calvin Goodrich 



on Peckerwood Shoals and disappears below Duncan's Riffle, Chilton Coun- 

 ty. Walkerii has a somewhat shorter range, Weduska Shoals, Shelby Coun- 

 ty, to Butting Ram Shoals, Coosa County. Five species occur at Wetumpka. 

 Their up-river range from this point is : Bxcistim, to Three-Island Shoals, 

 Talladega County ; laciniatum, to Fort William Shoals ; incisiim and piimilum 

 to Weduska Shoals ; pagoda, to The Bar, Chilton County. 



The localities for Gyrotoma mentioned in this paper are here set down 

 in their order, up-stream to down-stream, the county designations being 

 given as upon Mr. Smith's labels, though the river in most of these places 

 is the border between counties : 



Lock 2. St. Clair County. 

 Ten-Island Shoals. St. Clair County. 

 Lock 4, St. Clair County. 

 Riverside, St. Clair County. 

 Truss Shoals. St. Clair County. 

 Clarence Shoals, St. Clair County. 

 Hall's Island, Talladega County. 

 Yellowleaf Creek (upper), Shelby County. 

 Three-Island Shoals, Talladega County. 

 Fort William Shoals, Talladega County. 

 Peckerwood Shoals, Talladega County. 

 Weduska Shoals, Shelby County. 

 Cedar Island, Chilton County. 

 Adam's Ferry, Chilton County. 

 Yellowleaf Creek (lower), Chilton County. 

 Butting Ram Shoals, Coosa County. 

 Higgin's Ferry, Chilton County. 

 Wetumpka, Elmore County. 



Re;i,ationships and General Characters 



The affinities of Gyrotoma are with certain Goniobases which should 

 be separated from that genus. These mollusks are characterized by large 

 shells and large opert:ula. They have the same wide aperture of Gyrotoma 

 and the same microscopic sculpture. The group has not been carefully 

 studied, but these species unquestionably belong to it: Goniohasis impressa 

 Lea, laeta Jay, showalterii Lea (i860), lewisii Lea, bellula Lea and ovalis 

 Lea. Probably others are gratiosa Lea and lachryma Anthony, which Tryon 

 (10, pp. 342, 343) assigned to Eurycaelon. Occasionally all these species 

 develop incipient fissures. Mr. Smith collected several specimens with fis- 

 sures nearly as large as in pyramidatum and incisiim and yet, in other re- 

 gards, retaining their usual Goniobasic features. Every one has a deposit 

 of callus at the top of the columella. This is found in typical Gyrotoma. 

 One specimen of Goniohasis sho-walterii, in addition to having a very small 

 fissure, has a girdle for about 5 mm. upon the body whorl. 



After a little study it becomes apparent that Gyrotoma is not a compact 

 genus whose members can be traced with certainty to a common origin. It 

 differentiates into five natural groups. Pyramidatum and spillmanii form 

 one of these groups. A second consists of pagoda, pumilimi, alahamensis 

 and carinifenim. These two groups would appear to have developed from 

 Goniohasis laeta or some other species very like it. Lewisii and hender- 



