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STROBILOPSIDAE 



Family STROBILOPSIDAE 



The family Strobilopsidae is a group of small snails having 

 dome-shaped shells sculptured with oblique ribs. The shells 

 have 4^/^ to 6 slowly enlarging whorls and a distinctly open 

 umbilicus. The aperture is provided 

 with 2 or 3 parietal lamellae and sev- 

 eral long, narrow basal folds which 

 are deeply seated. 



This family is unlike all others in 

 the possession of peculiar basal folds, 

 which form a means of differentia- 

 tion between species. Each fold has a 

 definite position and name as indicated 

 in the figure of the aperture at the 

 bottom of this page. 



The animal of the Strobilopsidae 

 is very small for the size of the shell. 

 The head end of the body is black, the 

 posterior end is grayish and the foot 

 white. The tentacles are thick, bulb- 

 ous and rather short, and the eye pe- 

 duncles are short and thick, as is evi- 

 dent in the figure on this page of Strobilops labyrinthica, show- 

 ing a dorsal view of an animal of the Strobilopsidae. 



The Strobilopsidae may be found on decaying wood, under 



Parietal Lamella 



Interparietal Lamella 

 infraparietal lamella 



Columellas Lamella 



Palatal Fold 



Basal Folds 



loose bark and in similar situations. In North America, species 

 of this family have not been reported west of Nebraska and 

 Kansas, but east of this area they are abundant. 



