TORT U LOS A. 



2S5 





cyliudraceum, Chen). 

 Guatemalense, Pfeiff. 

 Guildingianum, Pfeiff. 

 MaDi, Poey. 

 Orbignyi, Pfeiff. 



pauperculum, Sow. 

 sectilabrum, Gould. 

 simulacrum, Morel. 

 tortuni, Wood. 

 ventricosum, D'Orb. 



Genus TORTULOSA, Gray. 



Operculum orbicular, flat, horny, many-whorled. 



Shell perforate, pupa-shaped, not callous, last whorl 

 furnished with a filiform, basal keel; aperture circular, entire, 

 prolonged at the base by a somewhat circular channel; 

 peristome continuous, dilated at its lower extremity into the 

 keel of the last whorl. 



Sy/i. Cataulus, Pfeiffer. 



Ex. T. tortuosa, Chemnitz, pi. 86, fig. 2. Operculum, 

 T. pyramidata, Pfeiffer, fig. 2, a, 2, b. 



This group, first indicated and named by Gray, and after- 

 wards described by Pfeiffer, seems to represent in Ceylon the 

 Megalomastoma of Guilding, which is principally limited 

 to the West-Indian Islands. The whorls of the operculum, 

 when macerated, separate, and may be unrolled in a spiral 

 form. 



Austeniana, Bens. 

 decora, Bens. 

 eurytrema, Pfe{ff\ 

 Layardi, Gray. 

 marginata, Pfeiff. 



Species of Tortulosa. 



pyramidata, Pfeiff. 

 Teuiplemaui, Pfeiff. 

 Thwaitesi, Pfeiff. 

 tortuosa, Chem. 



VOL. II. 



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