206 ODOSTOMIA. 



OBSOLETE, (obsoletus, lat.) Worn out, out of use. This 

 term is used to express an indistinctness of character, which 

 sometimes results from the action of sea-water upon unprotected 

 parts of the shell, and sometimes from the deposits of enamel 

 formed in age, and covering the early striae, ribs, teeth, &c. 

 thereby rendering them less acute. 



OBTUSE, (obtusus, blunt.) The application of this term is not 

 peculiar to conchology. It is most frequently used to express 

 the character of the spire. Ex. The apex of Megaspira, fig. 294. 



OCEANUS. Montf. (" Corne d' amnion vivant," Fr.) Nautilus 

 umbilicatus, Auct. 



OCTHOSIA. Ranz. Clitia, Leach. 



OCTOCERA. Bl. The first family of the order Cryptodibranchiata, 

 Bl. containing the genus Octopus. A species of which being 

 found in the Argonauta, or Paper Sailor, has given rise to the 

 long continued controversy as to whether it is really the constructor 

 of the shell, or whether it is a mere pirate, and having destroyed 

 the true animal of the Argonaut, has possessed itself of the 

 habitation. This question is now set at rest. See Argonauta. 



OCTOGONAL. (octogonum.) Having eight angles. For an exam- 

 ple, see Dentalium, fig. 2. 



OCTOMERIS. Sow. (oktw, octo, eight ; fiepog, 7neros, part ) Fam. 

 Balanidea, Bl. Order, Sessile Cirripedes, Lam. — Descr. Eight 

 principal valves circularly arranged, forming a compressed cone, 

 attached by a jagged base ; aperture eDclosed by an operculum, 

 consisting of four valves in pairs. — Obs. The only genus of Sessile 

 Cirripedes agreeing with this in the number of principal valves is 

 Catophragmus, Sow. which is, however, sufficiently distinguished 

 by the several rows of smaller valves by which the principals are 

 surrounded at the base. 0. angulosus, fig. 24. 



ODONTIS. Sow. Monodonta, Lam. 



ODOSTOMIA. Flem. Descr. " Shell conical ; aperture ov ate; 

 peristome incomplete, retrally, and furnished with a tooth on the 

 pillar.'' A genus composed of several small species of land 

 shells. Turbo plicatus, Spiralis, Unidentatus, &c. Mont. 



