68 THE LITTORINES. 



of time, and, except at high tide, they can always be 

 found upon the rocks along the shore. Each of the 

 little shells has a small spire of a few whorls, an 

 entire aperture, a sharp outer lip, and a thin, horny 

 operculum. 



Our first species, Littornia scutulata, Gld., Lit-to- 

 ri-na sku-tu-la'-ta, is shown in Fig. 52. The com- 

 mon name is, or ought to be, Checkered Lit- 

 torine, for that is what the Latin name means. 

 The shell varies in color from black to almost 

 white, but is usually of a greenish gray, with 

 more or less white bands or checks. Within 

 Fig. 52. the aperture, the shell has a purple tint. Its 

 length is from one-fourth to one-half of an inch, and 

 sometimes you find specimens even larger. 



Littorina planaxis, Nutt., plan-ax'-is, Gray Littor- 

 ine, is shown in Fig. 53. This species has a some- 

 what larger shell than the last, and is 

 easily distinguished by the flattened col- 

 umella, which seems to be dissolved away 

 by the animal in advance of the growing 

 whorl. The shells of this species are more 

 Fig. 53. rounded, and less finely colored than those 

 of the last species, but the two are often found closely 

 associated. 



The third Iyittorine, which is found in northern 

 waters, is named Littorina rudis, Don., ru'-dis, or 

 Rough Littorine. The shell of this bold northener, 

 in form and size, greatly resembles a large pea. It is 

 easily distinguished from planaxis by its rounded 

 columella, while its general surface, instead of being 

 nearly smooth, as in the last two species, is marked 

 by a good number of more or less developed spiral 



