GASTEROPODA PECTIN1BRANCHIATA. 53 



deposited with them. The figure of this envelope is often very 

 complex and singular*. 



Their tongue is armed witli little hooks, and by slow and repeated 

 rubbing u'-ts upon the hardest bodies. 



The great"-t difference in these animals consists in the presence or 



t' tin- little canal formed by a prolongation of the edge ot" 



the pulmonary cavity of the left side, and which passes through a 



similar canal or emargination in the shell, to enable the animal to 



it he without leaving its shelter. There is also this distinction 



between the genera some of them have no operculum; the species 



differ from each other by the filaments, fringes, and other ornaments 



of the head, foot, or mantle. 



These Mollusca are arranged in several families according to the 

 forms of their shells, which appear to bear a constant relation to that 

 of the animal. 



FAMILY I. 



TROCHOIDA, 



Tins family is known by the shell, the aperture of which is entire, 

 without an emargination or canal for a siphon of the mantle, as the 

 animal has none, and is furnished with an operculum or some organ 

 in place of itf. 



TROCHUS, Lin.f 



Have shells, the angular aperture of whose external border ap- 

 lies more or less to a perfect quadrangular figure, and in an 

 oblique plane, with respect to the axis of the shell, because the 

 part of the margin next to the spire projects more than the rest. Most 

 of these animals have three filaments on each edge of the mantle, or 

 at least some appendages to the sides of the feet. 



( M' tho>e tli ;t have no umbilicus, there are some in which the colu- 

 mella, tint lias the form of a concave arch, is continuous with the 

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

 tion of this mirgin which distinguishes them from Turbo Tecta- 



, Hi 'II. Molltf. N 



x, see Lister, 881, Baster, Op. Subs., I, vi, l, 2; for 



r,;i-trr. 10. V, 



I- Tin -y an- tin- r<ii::ccihulophora Diuini Asi/>h<>niihnnictniitit of liluiuvillc. 

 * (In- _ir;it LT< RUfl (.n.-;itr ,i!y (wiiiustuiiut, Biuiux. 



.:>.., V. d.\.\iii. 171213;- \iv, IJil; 



. 111.. r!\ii. i.-i.tiJ a7: TV. iii6riV//w, II.., 1532 3.' ; TV. M*r, Id., 

 rlvx. i -,7{_74; rr. rinensis, lb., 1564 65 ; Turlto payuths, 1.1., dxiii. 1541 

 42; Turbo tecti'.m-perricum, Ib., 1543 44. 



