LITTORINID^E. 231 



? Genus PORTLOCKIA, de Koninck, 1881. 



Turbiniform, imperforate ; spire somewhat elevated ; whorls con- 

 vex, with fine spiral ribs, some becoming larger on the last whorl ; 

 mouth oval, lip and columella thin. 



10 species. Devon, to Garb. ; Europe. P. PARALLELA, Phil. 



? Genus RHABDOPLEURA, de Koninck, 1881. 



Conical, height and diameter about equal ; whorls 4-5, slightly 

 convex, rapidly enlarging, the last more than half the total length, 

 spirally ribbed ; aperture transversely rounded, the inner lip some- 

 what callous, curved, and thickened below. R. SOLIDA, de Kon. 

 Carboniferous. 



Genus CREMNOCONCHUS, Blanford, 1869. 



Shell perforate, turbinately globose, spirally ribbed; aperture 

 subovate, margin simple, columella scarcely callous. Operculum 

 partly calcareous. 



Animal small, with short, thick proboscis, and long tentacles, 

 with eyes on swellings at their base, foot short and rounded at the 

 extremities, mantle margin finely crenulated. Dentition similar to 

 Littorina. Found in India, upon rocks wetted by fresh water. C. 

 SYHADRENSIS, Blanf. 



First described as Oremnobates, Blanford; preoccupied in ich- 

 thyology. 



Genus TECTARIUS, Valenc., 1833. 



Usually imperforate, turbinated or subconical, tubercular or mu- 

 ricate, periphery frequently angular or biangular; aperture striate 

 within, columella callous, subdentate at the base. Operculum pau- 

 cispiral, with a broad membranous border. The animal is like 

 Littorina : radula seven times the length of the shell, according to 

 Quoy. Tropical. 



T. PAGODUS, Linn. 



It is Pagodus, Gray, 1839, Pagodella, Swains, 1840. I am also 

 compelled to unite with this group, as synonyms, Nina, Gray, 1850, 

 and Echinella, Swainson, 1840; their characters being very vari- 

 able, and shading into those of the type. 



?Subgenus BRACHYTREMA, Morris and Lycett. 



I have described this form in Cerithiidse (see p. 113), but its re- 

 semblance to the present group is also very marked. 



