LIGIA. 443 



The outer antenna) are of considerable length, con- 

 sisting of a strong five-jointed peduncle, of which the 

 joints gradually increase in length, followed by a multi- 

 articulate flagellum, which, in our only British species, 

 contains thirteen or fourteen articuli, the last being ex- 

 tremely minute ; but in some of the exotic species as 

 many as thirty. The inner antennas are very minute, 

 flattened, and three-jointed. They are inserted close 

 together, just above the clypeus, and are not longer than 

 the basal joint of the outer pair. 



The body is oval and moderately convex, with the 

 seven segments well developed, the lateral portions, con- 

 sisting of the coxae, or first joint of the legs soldered to 

 the segments, being indicated by slightly impressed lines, 

 nearly parallel with the lateral margins, and being nearly 

 equally developed in all the segments. The tail consists 

 of six segments, of which the two anterior are distinct 

 on the middle of the back, but with the sides shortened 

 and concealed by the posterior direction of the lateral 

 extremity of the preceding segment of the body. The 

 third and two following segments of the tail are free, and 

 have their posterior angles acute ; whilst the terminal 

 segment has the posterior margin rounded, and on each 

 side the posterior angle is produced to a tooth. The ter- 

 minal pair of appendages are posteriorly exserted, and 

 are more or less elongated in various species. The basal 

 joint is truncated at its extremity, and furnished with a 

 pair of elongated cylindrical rami of nearly equal length 

 and size, the inner one terminated by a solitary strong 

 hair. 



The species are extremely active. They are very com- 

 mon on rocks just above high- water mark, hiding them- 

 selves in crevices of the rock and beneath stones with 

 great agility. 



