110 TYMPANOSTOMA. 
TURBINATED. (Turbo, a top.) Top-shaped. The term is ap- 
plied generally to those shells which are large at one extremity, 
and narrow to a point at the other. Hz. Trochus, fig, 358. 
Turbinellus, fig. 382. — 
TURBINEL’'LUS. Auct. (A little top.) Turbinated, thick, wide 
near the apex, generally tuberculated; spire short, depressed, 
mamillated; aperture rather narrow, terminating anteriorly in 
an open canal; outer-lip thickened within; columella, having 
from three to five prominent compressed, transverse folds. Obs. 
The Turbinelli are a well marked genus of marine shells, the 
species of which are numerous. No fossil species are known. 
The genus Cancellaria makes the nearest approach to Turbi- 
ninellus, in some characters, but may be distinguished by the 
roundness of its form, the raised lines inside the outer-lip, and 
the obliquity of the folds on the columella. Fig. 382 to 384. 
TURBO. Linn. (Atop.) Fam. Cricostomata, Bl, Turbinacea. Lam. 
Descr. Turbinated, solid, ventricose, generally grooved or tuber- 
culated; spire short, pointed; aperture generally rounded, sub- 
effuse anteriorly, entire; operculum shelly, solid, incrassated 
on the outer-side, horny and sub-spiral on the inner-side, Obs. 
The only certain means of distinguishing this extensive genus 
of marine shells from Trochus is the operculum, which in the 
latter genus is horny, spiral, and composed of a great number of 
whorls. The Trochi, however, are in general more conical, 
and flatter at the under side of the whorls, and this constitutes 
Lamarck’s distinction between the genera. T’. setosus, fig. 368. 
TURRICULA'CEA. Bl. The seventh family of the order Poly- 
thalamacea, Bl. containing the genus Turrilites. Fig. 483. 
TURRILITES. Lam. (Turris, a tower; duos, lithos, a stone.) 
Fam. Turriculacea, Lam. Ammonacea, Bl. Deser. Chambered, 
turrited, spiral; septa sinuous, and lobate, perforated by a si- 
phon; aperture rounded, with the outer-lip expanded. This 
genus, which is distinguished from the other Ammonacea, by 
having the spire produced, i. e. not being convolute, consists of 
several species, occurring only in the chalk marl. Fig. 483. 
TURRIS. Montf. A genus composedof such species of Mirra, 
Auct. as have the whorls angulated, with the aperture length- 
ened and undulated. 
TURRITELLA. Lam. (A little tower.) Fam. Turbinacea, Lam. 
Cricostomata, Bl. Descr. Turrited, elongated, generally grooved 
spirally ; spire pointed, consisting of numerous whorls; aperture 
rounded or angulated; inner and euter-lips thin, confluent an- 
teriorly ; operculum horny, Obs. The shells composing this well 
defined genus, are commonly called screws, aname to which the 
spiral grooves of most of the species seem to entitle them. Fig. 
370, T. imbricata. 
TYMPANOSTOMA. Schum. (Timbrel mouth.) Potamis Brongn. 
