356 MOLLUSCA. 



have three filaments on each edge of the mantle, 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, Avith 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 Avhich 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 columella^ most of them are flattened, and have 

 the external angle trenchant. Of this number is 



TV. agglutinans^'L.', Chemn., V, clxxii, 1688,9. Remarka- 

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



(1) Troth, inermis, Chemn., V, clxxiii, 1712 13; Tr. Coohii, Id., clxiv, 

 1551; Tr. cxlatus. Id., clxii, 1536 37; Tr. imbricatus, lb., 1532 33; Tr. 

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

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



(2) Turbo calcar, L., Chemn., V, clxiv, 1552; T.stellaris, 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. gi-anatum, lb., 1654 55; Tr. 

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

 clxviii, 1617 18; Tr. americanus, clxii, 1534 35; Tr. conulus, Gualt., 

 LXX, M. 



(5) Trochus concavus, Chemn., V, clxxviii, 1620, 21. 



(6) Trochus foveolaius, Chemn., V, clxi, 1516 19;' Tr. mauritianus, Id., 

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

 12. 



(7) Trochus telescopium, Chemn., V, clx, 1507 9. 



