THE SMALLER SEA-SHELLS 199 
is no wonder that many different names have been 
given to the varieties. In general the spire is 
short, the columella flattened, the outer lip thin, 
and the interior of the shell of a chestnut color. 
Sometimes the outside is smooth and almost black, 
sometimes the shell is light colored and coronated, 
but often it is of a dingy white, decorated with 
double spiral bands of dark brown, accompanied 
with spiral grooves. The Atlantic Purple, P. la- 
pillus, exhibits similar variations. 
Purpura lima, Mart., the Grooved 
Purple, Figure 208, is more rarely 
met with than the last species, prob- 
ably on account of its living in 
deeper water. The shell is commonly 
rather larger than that of the 
last species, while in appearance it 
is much more smooth and symmetri- 
eal. The spire consists of four By ie 
whorls, separated by distinct su- 
tures. The distinguishing feature, however, and 
the one which gives the name to the shell is the 
presence of about fifteen spiral grooves on the 
whorls, giving its surface somewhat of the appear- 
ance of a coarse file. The operculum, as in all the 
Purples, is thin, horny, and somewhat oval in 
shape. This is a very distinct species, and may 
be easily recognized by its rounded and channeled 
whorls. In the northern waters it is somewhat 
more similar to the last species, but a little care 
will usually easily separate them. 
