GASTEROPODA. 



243 



Shell like hittium ; proboscis retractile 

 nucleus apical. Eange 4 — 40 fathoms. 



operculum pointed, 



POTAMIDES, Brongniart. Presh- water Cerites. 



Etymology, potamos, a river, and ides, patronymic termination. 



Type, P. Lamarckii, Brong. (= Cerit. tuberculatum, 

 Brard.) 



Example, P. mixtus. PI. YIII., Pig. 19. 



Synonyms, TjTiipanotomus, Klein, C. fuscatum, Africa. 

 Pirenella, Eisso, C. mammillatum, PL YIIL, 

 Pig. 22. 



Shell like cerithium, but without varices in 

 the very numerous typical fossil species ; epi- 

 dermis thick, olive brown; operculum orbicular, 

 many-whorled. 



Distribution, 41 species. California, Africa, 

 India. In the mud of the Indus they are 

 mixed with species of ampullaria, venus, 

 purpii7'a, ostrea, &c. (Major W. E. Baker.) 



Fossil (species included with cerithium), 

 i]ocene — . Europe. 



Suh-genera, Cerithidea, Sw., C. decollata, 

 PL VIII., Pig. 24. Aperture rounded; lip 

 expanded, flattened. Inhabit salt marshes, 

 mangrove swamps, and the mouths of rivers ; 

 they are so commonly out of the water as to have been taken for 

 land-shells. Mr. Adams noticed them in the fresh waters of 

 the interior of Borneo, creeping on pontederia and sedges ; they 

 often suspend themselves by glutinous threads (Fig. 97). 



Distribution, India, Ceylon, Singapore, Borneo, Philippines, 

 Port Essington. 



Terebralia, Sw. Cerith. telescopium, PL VIII. , Fig. 21. 



Shell pyramidal; columella with a prominent fold, more or 

 less continuous towards the apex; and a second, less distinct, on 

 the basal front of the whorls (as in 7ierincea (Fig. 98). India., 

 North Australia. 



T. telescopium is so abundant near Calcutta as to be used for 

 horning into lime ; great heaps of it are first exposed to the sun, 

 to kill the animals. They have been brought alive to England. 

 (Benson.) 



Pijrazus, Montfort. Cerit. palustre, PL VIII., Fig. 20. 



Shell with numerous indistinct varices ; canal straight, often 

 tubular ; outer lip expanded. India, North Australia, 

 * C. obtusa, Lam. sp. copied from Adama. 

 M 2 



Fig. 97. Cerithidea.* 



