and is fusiform, or spindle-shaped ; that is, it is larger in the middle than 

 at either end, where it tapers to a point. Professor Parker suggested that 

 we examine the shell of this species, and see how it compared with that 

 of the fresh-water snails. This we did, and found that every part of the 

 latter could he found in the former. Here were the rounded whorls 

 revolving round the imaginary central axis, the oval aperture, the inner 

 and the outer lip, the columella, the suture and the umbilicus. We 

 noticed that this shell was roughened by many spiral lines which encir- 

 cled the whorls. In addition to these spiral lines were many fine lines 

 parallel with the edge of the outer lip and shaped like it. These were the 

 lines of growth, showing where the animal had added new matter to its 

 shell. Crossing the shell at right angles to the spiral lines, there were 



about twelve rounded ridges. These represented 

 the periods when the animal ceased adding to 

 the outer lip of the shell, and built this ridge or 

 varix. The Professor told us that some snails, 

 like the drill, build several of these ridges in a 

 single year ; but that others, as the rock shells 

 (Murex), build but three or four, and these are 

 highly ornamented, with frills and folds. The 

 aperture of the drill was tinted a dark purple, 

 and was very narrow at the lower end, and 

 formed a little canal through which the siphon 



Shell of the drill, Urosal- 



pinx cinereus, showing the was thrust. We learned that very irequentry 



different parts of the shell. ,1 i u J .c j.1 



a, apex; ac, anterior canal; there were two canals, one at each end oi the 

 ap, aperture; bw body whorl; aper t ure , called respectively the anterior and 



c, umbilicus; cl, columella; J 



il, inner lip; ol, outer lip; pc, posterior canals. "It is a curious fact," said 



posterior canal ; s, suture ; sp, . 



spire. (Biuney's Gould.) Proiessor Parker, that in most oi those shells 



having a canal in connection with the aperture, 



the animal is carnivorous, and lives by preying upon other animals, as 

 does the lion and the tiger, while in those shells with a rounded aper- 

 ture, the animal generally subsists upon vegetable food. 



" The mantle of the drill," continued the Professor, " as indeed of 

 other snails, is a closed sac which communicates with the water by means 

 of one or two siphons. The anterior siphon, which is extended through 

 the long anterior canal, is rather long and is generally reflected, or turned 

 back toward the shell. In some genera of snails there is a posterior siphon 

 of greater or lesser length, which extends through the posterior canal, and 

 expels the water from the gills in addition to the waste matter from the in- 

 testine. In a few snails, as Ctjprcva and Ovula, the posterior canal, instead 

 of being a mere notch, as in the drill, is extended in the form of a tubu- 



84 



