160 HELIX-LABRYINTHUS. 



granulate ; the color is chestnut or brown, sometimes with spiral 

 peripheral and subsutural darker zones. 



Key to species of Labyrinthus. 



[NOTE. In using the following Key, the shell should be held with the plane of 

 the aperture at right angles to the line of vision.] 



I. OUTER BASAL TOOTH BIFID. 

 a. Two inner basal teeth. 



Diam. over 30 mill. ; upper lip with a conical tooth bogotensis. 

 Diam. less than 25 mill. ; no tooth on upper lip. 



Spire depressed ; shell yellowish, banded with darker 



dunkeri. 



Spire low-conical ; shell unicolored, brown isodon. 



aa. One inner basal tooth, not bifid. 



Upper lip with a conical obtuse tooth otostoma. 



Upper lip not toothed 



Diam. exceeding 30 mill. bifurcata, furcillata, raimondii, 



\tarapotonensis. 

 Diam. less thnn 30 mill. 



Parietal tooth free from parietal edge of peristome 



yatesi, ellipsostoma. 

 Parietal tooth arising from parietal edge of peristome 



leprieurii. 



II. OUTER BASAL TOOTH NOT BIFID. 



a. Outer basal tooth flattened, transverse, entering, or hooked, the 

 parietal tooth pointing directly toward it or toward a point below 

 it on the outer lip. 



b. Acutely keeled ; lip with 2 teeth below the carina. 



Outer basal tooth flat, transverse, broad, nearly meeting 



parietal labyrinthus. 



Outer basal tooth smaller, conical or squarish plicata, 



Outer basal tooth with a projecting acute hook uncigera. 



bb. Acutely keeled ; lip with 3 teeth below carina ; parietal 



callous emarginate manueli. 



bbb. Obtusely keeled ; outer basal tooth deep-seated ; parietal 



callous straight. triplicata. 



aa. Outer basal tooth a small compressed tubercle on the lip, the 



parittal tooth directed toward a point above it on the peristome. 



Conoidal, thin, light ; teeth small ; one pit behind lip tamsiana. 



Depressed, dark ; teeth strong ; two pits behind lip leucodon. 



