TROCHUS. 279 



brought from the Mediterranean, Ceylon, the East and West 

 Indies, and South Seas. Fig. 398 to 401. 



TRITONIDEA. Sw. A genus of "Buccininae," Sw. thus de- 

 scribed : ' f Shell bucciniform, but the basal half is narrowed, 

 and the middle more or less ventricose ; spire and aperture equal. 

 Pillar at the base with two or three obtuse and very transverse 

 plaits, not well defined ; outer lip internally crenated and with 

 a superior siphon ; inner lip wanting*, or rudimentary." This 

 genus is the same as the one first distinguished by Mr. Gray 

 under the name of Pollia. We do not regret the discovery made 

 by Mr. Swainson of that name being previously occupied for a 

 genus of Lepidopterous Insects. Fig. 415, represents Tritonidea 

 articularis. (Pollia, Gray.) 



TRIVIA. Gray. A genus composed of those small species of 

 Cypr^a, Auct. which are characterized by small ridges on 

 the dorsal surface, and have the anterior of the columella inter- 

 nally concave and ribbed. C. Pediculus. Auct. fig. 449, 450. 



TROCHATELLA. Sw. A sub-genus of Helicinse, consisting of 

 those species which are acute and trochiform. 



TROCHIA. Sw. A genus of the family Buccininse, thus described : 

 ie shape intermediate between Purpura and Buccinum; whorls 

 separated by a deep groove ; inner lip when young, depressed, 

 when adult, thickened, convex and striated ; basal canal very 

 small. T. sulcatus. E. M. 422. f. 4." Sw. Malac. p. 300. 



TROCHIDON. Sw. A sub-genus of " Trochinse," Sw. Lardn. 

 Cyclop. Malac. p. 351. 



TROCHILjEA. Sw. ? Pileoltjs, Auct. 



TROCHURUS. Humph. Monodonta. Lam. 



TROCHUS. Auct. (A top.) Fam. Turbinacea, Lam. Gouiosto- 

 mata, 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 the 

 axis of the shell; operculum horny, orbicular, with numerous 

 whorls. — Obs> Lamarck distinguished this genus from Turbo by 



