200 THE LIFE OF CRUSTACEA 



terrestrial animals. Since there is reason to believe 

 that the Woodlice have been derived from marine 

 ancestors — they show no special affinities to the 

 fresh-water Isopoda, like Asellus — it is interesting to 

 find that the most primitive forms, which have de- 

 parted least from the general Isopod type, are 

 commonly found on or near the seashore. The 



Fig. 63 — The Sea-slater {Ligia oceanica). About Twice 

 Natural Size. (After Sars.) 



" Sea-slater," Ligia oceanica (Fig. 63), which is 

 abundant in rocky places on our own coast, is one 

 of the most primitive forms. It has a broad, flat- 

 tened, greenish-brown body, about an inch long, and 

 it runs quickly, creeping into narrow crevices of the 

 rocks, so that it is not easy to catch. The anten- 

 nules, as in the other land Isopods, are very minute, 

 but the antennai are long, and have, besides the five 



