GENERA OF SHELLS. 77 



Columella arcuated, more or less swelling at 

 base. Operculum. 



Many troclii have a brilliant, pearly surface, and sev- 

 eral have longitudinal ribs, which, we believe, are 

 never found in the turbo. 



T. iniperialis, longispina, Solaris, Indiens, radians, pileus 

 calyptrasformis, fimbriates, brevispina, rotularius, steJla, stel 

 laris, rhodostomus, spinulosus, costulatus, inermis, agglu 

 tinans, cœlatus, tuber, magus, merula, argyrostomus, Cookii 

 Niloticus, pyramidalis, noduliferus, coerulescens, obeliscus 

 virgatus, maculatus, granosus, squarrosus, incrassalus, flam 

 mulatus, elatus, marmoratus, mauritianus, imbricatus, trise 

 rialis, crenulatus, asperulus, acutus, fineatus, ziziphinus 

 conuloides, conulus, jujubinus, Javanicus, annulatus, dola- 

 rius, granulatus, granatuin, moniliferus, iris, ornatus, bicin 

 gulatus, calliferus, umbilicaris, undatus, Pharaonis, sagitti 

 ferus, carneolus, cinerarius, excavatus, nanus, pyramidatus 

 erythroleucos. 



MoNODONTA. Shell ovate or conical ; aper- 

 ture entire, rounded ; margins, disconnected 

 above ; columella arcuated, truncated at base. 

 Operculum. 



Distinguished from trochus chiefly by the more cir- 

 cular form of the mouth : from turbo by the columella 

 being truncated at base and forming the characteristic 

 tooth-like projection in the aperture. 



M.bicolor, pagodus, tectum-persicum, papilIosa,coronaria, 

 iEgyptiaca, carchedonius, modulus, tectum, labio, australis, 

 canalifera, viridis, fragaroides, constricta, tricarinata, articu- 

 Iata> lugubris, punctulata, canaliculata, seminigra, rosea, 

 lineata. 



Turbo. Shell conoid or subturreted ; out- 



