GASTEROPODS 373 
between tides. It is essentially a tropical species of very wide and ex- 
tended range, but it does not occur north of St. Augustine. At Tampa 
it has been found in vast numbers. (Plate LUXIX.) 
The California coast furnishes two more species of Littorina. Their 
station is among the rocks between tides, and their habits are quite the 
same as those of the east-coast species. 
L. scutulata. In this species the color is of various shades, gener- 
ally dark gray, mottled with white spots. A good-sized specimen 
measures one half of an inch in length. The spire is high; the 
columella flattened, broad; the shell is purplish-white within the 
aperture. (Plate LXIX.) 
EL. planaxis. Somewhat larger than the last; wider; with a 
lower spire; grayish in color, sometimes speckled with white; chest 
nut-brown within. The columella is remarkably flattened, and a 
portion of the whorl next bordering the columella is excavated as 
though eaten away by the animal. These two species are often found 
associated on the rocks. (Plate LXIX.) 
Genus Lacuna 
Closely allied to Littorina is the genus Lacuna, one species of 
which, L. vineta, is very abundant on the New England coast. 
A curious and distinguishing feature of this genus is the 
umbilicus, which forms a lengthened groove along the 
columella. LZ. vincta rarely exceeds one half of an inch 
in length, and is thin, with a pointed spire of five whorls. 
It is either of a uniform horn-color, or purplish, or banded = euna 
with chestnut. It may best be found upon marine plants 
in sheltered places, or may sometimes be gathered in quantity 
from the roots of Laminaria washed in by storms. 
Genus Tectarius 
The specific representatives of this genus are mostly tropical. 
T. nodulosus is abundant in Florida. It is about one half of an 
inch long, and has the flattened columella and round mouth 
characteristic of Littorina. It is decorated somewhat elaborately 
by revolving rows of nodules which cover the entire shell. Its 
station and habits are the same as those of Littorina. 
FAMILY CERITHODE 
In this family we meet with a somewhat new type of shell— 
the long, turriculate shell, with many whorls and with a channeled 
