Opisoma, Stoliez. . III 
Opisthobranchiata, II 
oe Il 
Opisthophorus, Bens. II 
Opisthoptera, Meek. III 
Opisthostoma, Blanf. IT 
Oppelia, Waagen. ._ II 
Optediceras, Leith. II 
Orbicella, d’Orb. . III 
Orbicula, Cuvier. . III 
Orbicula, Sowb. . III 
Orbicularius, Dumer. IIT 
Orbiculoidea, d’Orb. III 
Orbiculus, Megerle. III 
Orbisi ies! vehict apa EE 
Orbis, Schriter. . III 
Orbitima, Risso.. 2) <LI 
Orpulites, Lams). U1 
Oreula; Held... -.. LI 
Grinssa. Aide 2) Th 
Oriostoma, M.-C. .. II 
Ormoceras, Stokes. 1A 
Ornithopus, Gardner. IT 
 Orodoris, Bergh:.... II 
Orphnus, Albers. . III 
Orpiella,.Gray.. . LU 
Orthalicide. . ae LL 
Orthalicinus, C. & BEST 
Orthalicus, Beck. . II] 
Orthambonites, Pan. Lit 
Orthaulax, Gabb. . II 
Orthis, Dalman. . III 
Orthisina, d@’Orb. . III 
Orthoceras, Breynius. II 
oe ve IE 
Orthoceratites, Breyn. II 
Orthodesma, H. & W. IIT 
Orthodonta.-:-.. .. Tih 
ce 
Orthodontiscus,Mk. III 
Orthonema, M. & W. II 
Orthonota, Conrad. III 
Orthonychia, Hall. int 
Orthopoma, Gray. . II 
Orthostelis, Arad. . II 
Orthostoma, Desh.. II 
INDEX. 
PAGE : 
230 | Orthostylus, Beck. . 
Orthotetes, Fischer. 
Orthothrix, Geinitz. 
Orthotoma, Quenst. 
Orthotomium, C. & F. 
Orustia, Mirch. 
Orygoceras, Brusina. 
Oscanius, Gray. 
Oscilla, A. Ad. 
Osilinus, Phil. 
Ostomya, Conrad. . 
Ostrea, Linn. 
Ostreidie. ; 
Ostrenomia, Gonads 
Otala, Murch. 
Otala, M.-T. 
Otala, Schum. 
Otavia, Gray. . 
Otesia, H. & ae Ad. 
Preteens ears : 
Otina, Gray. 
Otinide. : 
Otoceras, Griesb. 
Otocheilus, Conr. . 
Otopoma, Gray. 
Otostoma, d’Arch. . 
Otostomus, Beck. . 
Otus, Risso. ..-:. 
Ovatella, M.-T. 
Ovella, Pfeiffer. . 
Ovulum, Bruguiere. 
Owenia, Prosch. 
Oxycheilus, Albers. 
Oxychilus, Fitzinger. 
oe vc 
Oxychona, Morch. 
Oxyegnatha. 
Oxygyrus, Benson. 
Oxynoe, Raf. 
| Oxynoticeras, Hyatt. 
Oxyperas, Mch. 
Oxystele, Philippi. 
Oxytes, Pfeiffer. 
Oxytoma, Meek. 
Ozena, Rafinesque. 
