128 



MANUAL OF THE MOLLrsCA. 



Tiiphoris, Dcshayes. C. perversum, PI. VTII.,. fig. 18. 30 sp. Norway 

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

 and posterior canals tubular. Tlie third canal is only accidentaUy present, 

 forming part of a varix. 



Cerithiopsis, Forbes. C. tuberculare, Brit. SheU like hittium ; proboscis 

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



PoTAMiDES, Brongniart. Fresb-water Cerites. 

 Etym., potainos, a river, and eidos, species. 

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

 Ex., P. mixtus. PI. VIII., fig. 19. 



Syn., tyn^panotomus, Klein, C. fuscatum, Africa. Pirenella, Risso, C. 

 mammillatum, PI. VIII., fig. 22. 



SheU like ceritbium, but without varices, in the very 

 numerous typical fossil species ; epidermis thick, olive- 

 brown ; operculum orbicular, many-whii-led. 



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

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

 venus, pm-pnra, vulsella, &c. (Major W. E. Baker.) 



Fossil (sp. included with ceritbium) Eocene—. 

 Europe. 



Sub-genera. CeritJiidea. Sw., C. decoUata, PI. VIII., 

 fig. 24. Aperture rounded: lip expanded, flattened. 

 Inhabit salt-mai'shes, mangi'ove 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. 78. 

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

 Terehralia, Sw. Cerith, Telescopium, PI. VIIL, fig. 21. 

 Shell pyramidal ; columella vaih. a prominent fold, more or less continuous 

 towai'ds the apex ; and a second, less distinct, on the basal front of the whirls 

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



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

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

 They have been brought alive to England (Benson). 

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

 Shell with numerous indistinct varices ; canal straight, often tubular ; 

 outer lip expanded. India, N. Australia. 



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

 nearly the fossil ^iotamides, but they have numerous vaiices. 



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



Fig. 78. Cerithidea. 



