SHELLS WITHOUT CANALS 215 
Turritella cooperi, Cooper’s Tower- 
shell, Figure 231. This southern species 
has a very slender, many-whorled spire. 
The sutures are distinct, the aperture 
circular, and the outer lip sharp and 
thin. The color is yellowish, somewhat 
spotted with brown. It can hardly be 
mistaken for any other shell. It is found 
on sandy beaches between tides. 
Tachyrynchus (Mesdlia) tenuisculp- 
tus, Cpr., the Little Tower-shell, is like 
a minute specimen of the last, and is 
found on mud-flats along the southern coast. The 
usual length is less than one-fourth of an inch. 
When you went to the seacoast, and climbed 
among the rocks where the waves were throwing 
up their spray as the tide was coming in, you 
surely saw numbers of dark-colored shells about 
the size of peas. You found them in the eracks of 
the rocks, along their sides, and concealed in every 
little nook and cranny. Their shells are dull in 
color, somewhat like the rocks themselves, the 
apertures are closed with horny operecula, and the 
animals seem to be asleep. But put some of them 
into a jar of sea-water, and soon the little black 
snails come creeping out, and begin to work their 
way up into the air again. 
These little Littorines, as we will call them, are 
the first mollusks we meet as we go down to the 
shore. The upper part of the beach is known as 
the littoral region, so you see how the mollusks get 
the name of Littorine. They live out of the water 
