128 



MA^'^UAL OF THE MOLLUSCA. 



Triphoris, Deshayes. C, perversura, PI. VIII., fig. 18. 30 sp. Norway 

 — Australia. Fossil. Eocene — . Brit., France. Shell sinistral; anterior 

 and posterior canals tubular. The third canal is only accidentally present, 

 forming part of a varix. 



Cent]uoj)sis, Forbes. C. tuberculare, Brit. Shell like hittium ; proboscis 

 retractUe ; operculum pointed, nucleus apical. Range 4 — 40 fms. 



PoTAMiDES, Brongniart. Fresh-water Cerites, 

 Eti/m., potmnos, a river, and eidos, species. 

 Ti/pe., P. Lamarckii, Brong. (= Cerit. tuberculatum, Brard.) 

 JEz\, P. mixtus. PI. VIII., fig. 19. 



Si/n., tympauotomus, Klein, C. fuscatum, Africa. Pirenella, Risso, C. 

 mammillatum, PL VIIL, fig. 22. 



Shell like cerithium, but without varices, in the very 

 numerous typical fossil species ; epidennis tliick, oHve- 

 brown ; operculum orbicular, many-whirled. 



Distr., old world only ? Africa, India. In the mud 

 of the Indus they are mixed with sp. of ampullaria, 

 venus, purpura, vulsella, &c. (IMajor V^'^. E. Baker.) 



Fossil (sp. included with ceritliium) Eocene — . 

 Europe. 



Sub-genera. Cerithidea. Sw., C. decollata, PI. VIII., 

 fig. 24. Apertm-e rounded : lip expanded, flattened. 

 Inhabit salt-marshes, mangi-ove swamps, and the mouths 

 of rivers ; they are so commonly out of the water as to 

 have been taken for land-sheUs. 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. 78. 

 Distr. India, Ceylon, Singapore, Borneo, Philippines, Port Essington. 

 Terebralia, Sw. Cerith, Telescopium, PI. VIIL, 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 whirls 

 (as in nerincea, fig. 79). India, N. Australia. 



T. telescopimn is so abundant near Calcutta, as to be used for burning 

 into lime ; great heaps of it are first exposed to the sun, to kill the animals. 

 They have been brought alive to England (Benson). 

 Fyrazus, Montf. Cerit, palustre, PI. VIIL, fig. 20. 

 Shell with numerous indistinct varices ; canal straight, often tubulai' ; 

 outer lip expanded. India, N. Australia. 



Cerith radulum and granulatum of the W. African rivers approach very 

 nearly the fossil potamides, but they have numerous vai'ices. 



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



Fig. 78. Cerithidea. 



