2 ALATA, 
flected lip. The Polyphemi of Montf. have an undulation in the 
outer lip. A. Virginea, fig. 286. Polyphemus Glans, fig. 288. 
ACHATINELLA. Sw. Is a small group of shells, differing 
from Achatina in having the inner edge of the outer lip thick- 
ened, and a slight groove near the suture of the spire. Fig. 287. 
ACHE'LOIS. Montf. Conmurres Achelois. Knorr. Sup. t. iv. fig. 1. 
ACIONA. Leach. Scanaria, Auct. 
AC’TCZHON. Montf. Tornateia, Lam. 
AC’TINOCAMAX. Stokes. A genus of Belemnitiform fossils. 
ACUMINATED. Terminating in a point, as the apex of Me- 
lania Subulata, fig. 313. 
ADDUC’TOR MUSCLE. That which draws the two valves of 
a shell together, and leaves a mark in the inner surface of each, 
called the MuscuLar IMPRESSION. 
ADELOSINA. D’Orb. A genus of microscopic Foraminifera. 
ADESMA’CEA. Bl. (a, without; Aesua, desma, a ligament.) The 
tenth family of the order Lamellibranciuata, B\. composed of Mol- 
lusea, which either bore tubular dwellings in rocks, wood, &c., or 
live in testaceous tubes; their shells being consequently destitute 
of the hinge ligament. The action of opening and shutting 
the valves being limited by the narrow space in which they are 
confined, or else the valves themselves, being soldered into the 
tube, renders it unnecessary for them to have a ligament, to keep 
them in their places. The genera Pholas, Teredina, Teredo, 
Fistulana and Septaria, belong to this family. 
ADNA. Leach. One of the genera separated by Leach from 
Pyrgoma, and characterized as consisting of a single upper 
valve, supported ona funnel shaped base, which is not buried in 
the coral to which it is attached, like Pyrgoma, but is seen exter- 
nally. The operculum consists of four valves. Adna, fig. 32. 
AGAN'IDES. Montf. Orsuuires, Lam. 
AGATHIR’SES. Montf.  Siliquaria Muricata, Auct. 
AK’ERA. A genus of extremely light, horny shells resembling 
Bua, from which it differs, in the outer lip being separated from 
the body whorl, and consequently elastic. Ez. Bulla Fragilis, 
fig. 247. 
AK'ERA. Bl. The fourth family of the order Monopleurobranchi- 
iata. Bl. containing the genera Bulla, Bulleea and Bellerophon. 
ALAA. Jeffreys. A genus of minute land shells, resembling 
Vertigo, but separated because they are dextral, while Vertigo 
is sinistral. Ez. Fig. 292. A. Marginata; Pupa Marginata, Drap. 
found in marshy ground, roots of trees, moss, &c. 
ALASMODON. Say. Division of Unio, consisting of such 
species as have cardinal, but no lateral, teeth. Hx. A. Compla- 
natus, fig. 141. 
ALATA. Lam. (From Ala, a wing.) A family belonging to 
the second section of the order Trachelipoda, containing the 
