9 



Section MICROCYSTINA, Morch, 1872. 



Shell small, polished, with a deep notch at the columellar 

 margin. 



Animal like Microcystis. India. 



Section SAGDINELLA, Morch, 1872. Nicobar Islands. 



Section THAPSIA, Albers, 1860. 



Shell orbicularly depressed, thin, pellucid, undulateiy decus- 

 sated, narrowly perforated ; peristome acute, eoluniellar margin 

 narrowly reflected. West Africa. 



Section LAMPROCYSTIS, Pfeffer. India, Polynesia. 



Section OXYTES, Pfeitter, 1855. 



Shell usually large, obliquely striate or plicate, depressed, 

 carinated, umbilicated ; peristome expanded, thin, columellar 

 margin thickened. 



Animal with short somewhat thickened tentacles ; mucous 

 gland without marked appendage ; right cervical lobe triangular, 

 well developed, left lobe bipartite, anterior portion large, pos- 

 terior very small and giving off short processes ; left shell lobe 

 a narrow ribbon, reflected over the peristome, no right shell 

 lobe. India. 



Subgenus SESSARA, Albers, 1860. 



Shell imperforate, depressed orbicular, costulate-striate above, 

 base smooth, excavated, periphery angulated; aperture depressed, 

 wide, basal lip denticulated, columellar thickened. 



Mantle lobes small, but as in Xesta. Burmah. 



Subgenus GUILLAINIA, Bourguignat. 



Shell thick, calcareous, strongly striate or costulate, globular, 

 bluish white, peristome simple, obtuse, interior dark chocolate- 

 colored. 



Animal with a large profound mucous pore with horn-like 

 appendage. Dentition and jaw as in Hyalina. 



The shell reminds one of the genus Leucochroa. East Africa. 



Genus ZON1TES, Montfort, 1810. 



Shell subdepressed, umbilicated, very thin, more or less trans- 

 parent ; aperture semilunar, usually without teeth; lip thin, 

 sharp. 



