356 MOLLUSCA. 



have three filaments on each edge of the matitle, or at least some 

 appendages to the sides of the feet. 



Of those that have no umbilicus, there are some in which the co- 

 lumella, that has the form of a concave arch, is continuous with the 

 external margin, without any projection. It is the angle and projec- 

 tion of this margin which distinguishes them from Turbo — Tecta- 

 RiUM, Montf.(l) 



Several are flattened, with a trenchant edge, which has caused 

 them to be compared to the rowel of a spur — Calcar, Montf.(2) 



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

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

 Lam. (3) 



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 Trochi 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.(4) 



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

 than it is high, and their convex base approximates them to the Ca- 

 lyptracea — Infundibulum, Montf.(5) 



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

 high, the columella forms a spiral canal(6). 



Those which have a turreted shell approach Cerithium — Tele- 

 scoPiuM, Montf.(7) 



Among the umbilicated Trochi, there are some in which there is 

 no projection in the columellaj most of them are flattened, and have 

 the external angle trenchant. Of this number is 



TV. agglutinans^h.; Chemn., V, clxxii, 1688,9. Remarka- 

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



(1) Troch. incrmis, Chemn., V, clxxlii, 1712 — 13; — Tr. Coohii, Id., clxiv, 

 15515 — Tr. cxlatus. Id., clxii, 1536 — 37; — Tr. imbricatus, lb., 1532 — 33; — Tr. 

 tuber. Id., clxv, 1573 — 74; — Tr. sinensis, lb., 1564 — 65; — Turbo pagodus. Id., 

 clxiii, 1541 — 42; — Turbo tectum-persicum, lb., 1543 — 44. 



(2) Turbo calcar, L-, Chemn., V, clxiv, 1552; — Tstellaris, Id., 1553; — T acu- 

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



(3) Tr. vestiarius, L., Chemn., V, clxvi, 1601. 



(4) Tr. iris, Chemn., 1522— 23;— Tr. granatum, lb., 1654 — 55;— Tr. 

 zyzyphinus, lb., clxvi, 1592 — 98; — Tr. conus, clxvii, 1610; — Tr. maculatus, 

 clxvlii, 1617 — IB; — Tr. americanus, clxii, 1534 — 35; — Tr. conulus, GuaU., 

 LXX, M. 



(5) Trochns eoncavus, Chemn., V, clxxviii, 1620, 21. 



(6) Trochus foveolatus, Chemn., V, clxi, 1516 — \9\ — Tr. muuritianus, Id., 

 clxiii, 1547— 48;— Tr. fenestratus, lb., 1549— 50;— Tr. obeliscus, clx, 1510 

 —12. 



(7) T roehus tele scop) uni, Cliemii., V, clx, 1507 — 9- 



