20 THE MACRONS. 



in a different sense by some writers, so in the begin- 

 ning I would clearly define what is meant by the 

 terms to be used. 



In Fig. 2 we have a picture of the shell of a little 

 mollusk which lives on the above-mentioned southern 

 coast. Its name is Macron lividiis^ A. Ad., 

 Mak-ron liv^-id-us. The shell is small, seldom 

 more than an inch in length, without sculp- 

 ture, and of a brownish color. When found 

 living it is covered with a brown epidermis, 

 which is laid on in little ridges, and resem- 

 Fig- 2. bles a coating of fine, soft cloth. 

 We shall often have occasion to speak of the epi- 

 dermis or outside coating of the shell. In this species 

 it is very persistent, that is, it clings to the shell and 

 covers it from the apex to the canal. In many species, 

 however, it is easily removed ; and when specimens 

 have been knocked about a little their epidermis is 

 nearly lost. Still other shells, like the smooth Olives, 

 show scarcely a trace of epidermis. 



The shape of our Macron is well shown in the 

 figure ; the whorls are five in number, the outer lip 

 sharp and curved, and the canal short and bent. 



The position to hold a shell for study is shown in 

 the figure. The apex should be uppermost, and the 

 axis, or the line which may be supposed to run through 

 the center of the whorls, should be vertical. In this 

 way the spire becomes the upper part of the shell, 

 and we know that it is the oldest part, while the canal 

 is the lowest portion. The French usually draw their 

 figures of shells with the apex downward, but they 

 observe the same rule in regard to the vertical axis. 



Notice the strong white fold on the inner wall 

 near the top of the aperture ; it is a characteristic 



