TETEADECAPODA. 



363 



FIG. 492. 



the three anterior in another series ; and their branchiae 

 are abdominal. 



Many of the marine species are parasitic in their habits. 

 Some kinds live in fresh waters. Those called Wood-lice 

 (Oniscus) and the Pill-bugs (Armadillo} live on the land 

 in damp cellars, aud under rubbish in damp places. 



The AMPHIPODA, as the Sand-fleas (Orchestra, Talitrus, 

 and Gammarus\ have the thoracic legs in two series, and 

 the four anterior pairs are di- 

 rected forwards, and the three 

 posterior pairs backward. And 

 their respiratory organs are in 

 the form of membranous vesi- 

 cles, attached to the base of the 

 legs. The name is from the 

 Greek amphi, both, and pous, 

 foot, and may refer to the fact 

 that the Amphipods have botli 

 thoracic and abdominal append- Beach ' pr s - an<J - FIea > Talit l st - 

 ages, or to the fact that in the legs are combined both 

 locomotive and respiratory organs ; or to the fact that the 

 feet are arranged in two series, one pointing forward, 

 and the other backward. 



FIG. 493. 



Caprella geometrica, Say. 



The "Whale-lice (Cyamus), Caprella, etc., are crustaceans 

 which bear a resemblance to the Amphipods in the ar- 

 rangement of the respiratory organs, but differ in having 



