OPERCULINA. 73 
ing destroyed the true animal of the Argonaut, has possessed. 
itself of the habitation. 
OCTHO'SIA. Ranz. Curia, Leach. 
OCTOLAS MIS. Gray. Hzpratasmis, Leach. (oxro, octo, eight; 
éhacpos, elasmos, plate.) Fig. 41, O. Warwicku. 
OCTO’MERIS. Sow. (oxro, octo, eight; pps, meris, part.) Fam. 
Balanidea, Bl. Order. Sessile Cirripedes, Lam. Descr. Hight 
principal valves circularly arranged, forming a compressed cone, 
attached by a jagged base; aperture enclosed 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 distin- 
guished by the several rows of smaller valves by which the 
principals are surrounded at the base. O. angulosus, fig. 24. 
ODON’TIS. v. Monoponta. 
ODOSTOMIA. Flem. JDescr. “ Shell conical; aperture ovate ; 
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. 
OLIVA. Auct. (An olive.) Fam. Convoluta,Lam. Angyostomata, 
Bl. Deser. Oblong, cylindrical, thick, smooth, shining ; spire 
very short, with sutures distinct; aperture elongated, notched at 
both extremities; outer-lip generally thick; columella thick, 
obliquely striated, terminated by a tumid, oblique, striated 
varix ; a raised band passing round the lower part of the body 
whorl. Obs. The shells composing this well known genus 
present a great variety of rich markings and brilliant colours. 
They are Marine. Fossil species are found sparingly in the 
London Clay and Calcaire-grossiér. The Ancillariz are dis- 
tinguished from this genus by the sutures of the whorls being 
covered by enamel. O. maura, fig. 457. 
OLIVEL'LA. Sw. One of the genera separated from Ourva by 
Swainson, and described as having two basal plaits on the colu- 
mella. 
OLYGY’RA. Say. Mentioned by Rang as properly belonging 
to Helicina. H. neritella, Auct. 
OMALAX'S. Desh. Subsequently Birrontia, Desh. Fig. 354. 
ONIS’CIA. Lam. Fam. Purpurirera, Lam. Entomostomata, 
Bl. Deser. Oblong, sub-ovate, slightly turbinated, cancellated ; 
spire short; aperture elongated; terminating anteriorly in a 
very short, scarcely recurved canal; outer-lip thickened, den- 
ticulated within; inner-lip spread over a portion of the body 
whorl, granulated. Obs. The granulated inner-lip is the princi- 
pal character by which this genus is distinguished from Cassi- 
daria. In Oniscia the canal is not so produced. O. oniscus, 
fig. 409. 
OPERCULINA. D’Orb. A genus of microscopic Foraminifera. 
L 
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