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 LXIX.) 



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. 



. 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.) 



L. 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. vincta, 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. L. 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 

 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 CEBITHIIDJE 



In this family we meet with a somewhat new type of shell 

 the long, turriculate shell, with- many whorls and with a channeled 



