108 TROCHUS. 
grooved sides, two similar teeth in the other; ligament external, 
thick; muscular impressions, two in each valve. Obs. Only one 
recent species of this marine genus is known; the T. pectinata, 
which comes from New Holland, and was formerly so rare, that 
a very much worn odd valve has been known to produce a con- 
siderable sum. It is of a brilliant pearly texture within, tinged 
with purple or golden brown. Fossil species abound in Lias, 
Upper and Lower Oolites, and green sand. T. pectinata, fig. 
139. 
TRIGONOSE’MUS. Konig. A genus composed of species of 
TEREBRATULA, Auct. which have one valve produced into a 
beak, perforated, or, as it were, truncated at the apex. T. 
lyra, fig. 208, differing from Terebratula lyra, Lam. 
TRIGONOTRE'TA. Konig. A genus composed of species of 
Terebratula, Auct. which have the hinge of the larger valve pro- 
duced into a triangular disc, divided by a triangular foramen in 
the centre. Spirifer, Sow. belongs to this genus. Fig. 214, 215. 
TRILOBATE. (cpua, tria, three ; doBos, lobos, division, part, lobe.) 
Divided into three lobes or principal parts. Ex. Malleus, Fig. 
165. 
TRILOCULI'NA. D’Orb. A genus of microscopic Foraminifera. 
TRIPHOR’A. Deshayes. A genus composed of small sinistral 
species of Crrituium, Auct. with the anterior canals closed 
at the bases and open at the extremities; so as to present the ap- 
pearance of a threefold aperture. Fig. 375. 
TRIP’'LODON. Spix. Hyria, Lam. 
TRIP’TERA. Quoy et Gaimard. Cuvizrim, Fer. ? 
TRIQUE’TRA. Bl. Triangular species of Venus, Auct. 
TRISIS. Oken. Anca Tortuosa, Auct. 
TRITON. Auct. Fam. Siphonostomata, Bl. Canalifera, Lam. 
Descr. Oblong or oval, thick, ribbed or tuberculated, with dis- 
continuous varices placed at irregular distances ; spire prominent, 
mamillated ; aperture round or oval, terminating anteriorly 
in a generally long, slightly raised canal; columellar lip granu- 
lated or denticulated ; outer-lip thickened, reflected, generally 
denticulated within; epidermis rough; operculum horny. Fig. 
398 to 401. 
TRI'VIA. Gray. A genus composed of the small species of Cy- 
prea, Auct. which are characterized by small ridges on the 
dorsal surface, and have the anterior of the columella internally 
concave and ribbed. C. Pediculus, fig, 449, 450. 
TROCHI'LAA. Sw. Pirzoivs, Auct. 
TRO'CHUS. Auct. (A top.) Fam. Turbinacea, Lam. Gonios- 
tomata, Bl. Descr. Turbinated, thick, striated, tuberculated or 
smooth : spire elevated, conical, consisting of numerous whorls ; 
under surface discoid; aperture more or less depressed in an 
oblique direction, generally angular; columella arcuated, more 
or less prominent at its union with the outer-lip, contiguous to 
