14 University of Michigan 



mens). All of the shells are unicolor. The growth lines are 

 markedly definite and regular; in some cases, spiral lines are 

 also quite prominent, hut this character is variahle. The short 

 (.5 mm.), reddish-hrown hairs are often removed with the in- 

 crusting dirt, hut, in perfect specimens, are arranged so as to 

 form spiral rows and also rows parallel to the growth-lines. 

 The heavy, hasal callus has a peripheral thickening, where it 

 appears as a projection at the hase of the columella. In young 

 specimens, just outside of this projection is a definite, triangu- 

 lar slit, which is represented hy a well-marked indentation in 

 fully mature shells with slightly reflected and thickened peri- 

 stome. The heavy and well-developed, calcareous plate of the 

 operculum is similar to that of O. scricca (Cf. Wagner, 1907, 

 X-4), but bears a more definite, longitudinal ridge on the inner 

 surface, running from the nucleus to the basal angle. The an- 

 gular region is also especially thickened. The very thin, horny 

 plate is slightly pinkish in color; during removal of the animal, 

 it is usually separated from the calcareous plate, as it adheres 

 closely to the foot. 



The type belongs to the brown color-form, and was collected 

 on leaves of trees near La Fria (H, II, d, 40). 



Whorls Height Maj. Diam. Min. Diam. 



100 (5.0) Wagner, (1907) 

 125 (6.2) Pfeiffcr (1854) 

 119 (5.7) Aracataca, Col. 

 114 (6.4) Female (type), 

 no (5.5) Male. 



'J'he radular f(jrmula of O. r. tiu-Jiirciisis is given in ancjther 

 paper (1922), and characteristic teeth are figured here (fig. 

 iii-14). 'J'he very broad, rachidian plate distinguishes it from 

 Alcadia s. s. Other species of Oligyra from northern South 

 America are: O. (Analcadia) dysoni dysoui (Pfr., 1859), 



