54 MOLLrSCA. 



Several are flattened, with a trenchant edge, which has catised them 

 to be compared to the rowel of a spur — Calcar, Montf.* 



Some again are slightly depressed, orbicular and sinning, with a 

 semi-round aperture, the columella convex and callous — Rotella, Lam.f 



The columella of others is distinguished near the base by a little 

 prominence, or vestige of a tooth, similar to that of the Monodontes, 

 from which these Trcchi only differ in the angle of their aperture, 

 and the projection of their margin. The aperture is usually about 

 as high as it is wide — Cantharis, Montf.;]: 



In some of them, on the contrary, the aperture is much wider than 

 it is high, and their convex base approximates tliem to the Calyp- 

 tracea — Infundibulum, Montf. § 



In others again, where the aperture is also much wider than it is 

 high, tke columella forms a spiral canal ||. 



Those Avhich have a turrcted shell approach Cerithium — Telesco- 

 piiim, Montf,^ 



Among the umbilicated Trochi, there arc some in Avhich thei'e is no 

 projection in the columella ; most of them are flattened, and have the 

 external angle trenchant. Of this number is 



Tr. agghitinans, L. ; Chcmn., V, clxxii, 1688, 9. Remarkable 

 for the habit of glueing to its shell, and even incorporating 

 with it, as fast as it increases in size, various foreign bodies, 

 such as little pebbles, fragments of other shells, &c. ; it frequently 

 covers its umbilicus with a testaceous plate **. 



The margin of others, however, is rounded, such as 



Tr. cinerarius, L.; Chemn., V. clxxi, 1686. A small species, 

 and the most common on the coast of France; greenish, ob- 

 liquely streaked with violet. 



Some umbilicated Trochi have a prominence near the bottom of 

 the columella f f . 



And, finally, there are others in which it is longitudinally cre- 

 nate+|. The 



* Turbo calcar, L., Chemn., V. clxiv, 1552; — T. sfellaris, Id., 1553; T. aculeafv.s, 

 Id., 1554 — 57; — T. imperialis, Id., 1714. 



f Tr. vestiariits, 1,., Chemn., \. clx\\, \60l. 

 g I Tr. h-is, Chemn., 1522 — 23; — Tr. (jranafiim, lb., 1654 — 55;— Tr. zyzt/phinus, 

 lb., clxvi, 1592 — 98; — Tr. comts, clxvii, 1610; — Tr. macuhifus, clxviii, 1617 — 18 ; — 

 Tr. amencams, clxii, 1534 — 35; — Tr. cmnihts, Gualt., LXX, M. 



§ Trochus concarus, Chemn., Y, clxxviii, 1620, 21. 



II Trochus foveolatiis, Chemn., V, clxi, 1516 — 19; — Tr. mauntiamts, Id., clxiii, 

 1547 — 48 ; — Tr.fcnesfrafus, lb., 1549 — 50; — Tr. obelisciis, clx, 1510 — 12. 



^ T)-ochus felescopium, Chemn., V, clx, 1507 — 9. 



** Add, Trochus Judicus, Chemn., \, cLxxii, 1697 — 98; — Tr. ImperiuUs, clxxiii, 

 1714, and clxxiv, 1715;— Tr. Solaris, lb., 1701 — 1702, and 1716— 1717 ; — Tr. 

 planus, lb., 1721, 1722. 



ft Tr. virgatus, Chemn., V. clx, 1514 — 15 ; — Tr. nilotkvs, Chemn., V. clxvii, 

 1605 — 7, cLxviii, 1614; — Tr. vernus, Id., clxix, 1625 — 26; — Tr. inetquulis, clxx, 

 1636 — 37 ; — Tr. magnus, clxsi, 1656 — 57 ; — Tr. conspersus, Gualt., Ixx. B. ; — Tr. 

 jujubinus, clxvii, 1612 — 13. 



XI Tr. maculatus, chiviii, 1615 — 1616; — Tr. cosfufus, dxix, 1634; — Tr. dridis, 

 clxx, 1644; — Tr. radiatus, lb., 1640 — 42. 



