JI2 



Calvin Goodrich 



stream, becoming modified through isolation and the influences of creek 

 •conditions. Brcznspira is still farther away from taeniata, presenting in part 

 aspects common to auipla of another group and possessing a dimorphism 

 peculiar to itself. Aldrichi I believe to be a derivative of griffithiana as also 

 flexuosa, a puzzling form which supports the suspicion of hybridization 

 more than any other species among the Alabama Anculosae. 



The three members of the compacta group — compacta, mclanoides and 

 z'ittata — are small unsculptured mollusca, one living in Cahaba River, the 

 second in the Black Warrior and the third in the Coosa. Compacta was 

 recognized as a Lithasia by Tryon, but it is as truly an Anculosa as is 

 mclanoides, which it resembles. In shell characters the first two are alike, 

 but as regards the opercula the affinities are closer between the second and 

 third than between either of these and compacta. 



Anthony's ligata constitutes a group to itself. It has no close relation- 

 ships with any other living Anculosa and its operculum is unique. 



The relationship of the members of the ampla group to one another is 

 quite clear. Mhnica is a creek form of ampla, confined to one stream so 

 far as is known, which has become uniformly smaller, has intensified the 

 parent sculpture and acquired a distinctive banding formula that involves 

 more than 50 per cent of the collected shells. Plicata can be conceived as 

 the living representative of emigrant ampla of long ago which went into the 

 Black Warrior and the Tombigbee rivers. The small creek species smithi 

 links with plicata. The whole group is compact, well characterized. Yet 

 the gap between it and the taeniata group is vague. Conic forms of ampla, 

 taken by themselves and lacking as they often do the flattened columella 

 most strongly marked in juvenile and half-grown specimens, might easily 

 be confused with taeniata. There is also a certain amou^i; of resemblance 

 in the opercula. 



The sJioii'alterii group is less compact than the preceding one. Both 

 shozvaltcrii and sulcata have smooth or nearly smooth forms, and seem 

 then to belong to the taeniata group. Certain rather rare forms of griffi- 

 thiana copy lirata and only because there exists a long gap in the river be- 

 tween the two races the species might justly be brought close together. 

 The opercula are wanting in distinctiveness, resembling most those of the 

 taeniata group. Yet the deeply sulcate character of the mass of these three 

 species seems to warrant their separation into a group to themselves. They 

 are besides common to one fairly short stretch of the Coosa River whereas 

 the members of the taeniata clan are more widely scattered. Occultata is 

 joined to this group on the ground of its sulcata-Wko. operculum and the 

 flaring jjcristome which is a well-marked feature of young shoivaltcrii. Mr. 

 Smith also placed it here. 



