454 CRUSTACEA. 



live principally in transparent marine animals, especially in Medusas, 

 and may, as the female Phronima sedentaria, take up their abode 

 with their entire brood in transparent Pyrosoma, whose internal 

 parts they eat up. The Cyamidce among the Lcemodipoda are 

 parasitic on the skin of whales. 



Tribe 1. Laemodipoda. 



Amphipoda with cervically placed anterior legs and rudimentary 

 apodal abdomen. 



The anterior thoracic segment is more or less closely fused with 

 the head and the anterior pair of legs shifted on to the neck. The 

 maxillipecls are modified to form a quadripartite under-lip with long 

 palps. The branchiae are usually confined to the third and fourth 

 thoracic segments, the legs of which are often rudimentary or are 

 altogether wanting. The feet end with hooks for attachment. The 

 abdomen is small and reduced to a short protuberance destitute of 

 appendages. 



Caprdla linearis L. Body elongated and thin. They are parasitic on Hydroids 

 and colonies of Bryozoa. Cyamus ceti L. Body broad and flat ; abdomen quite 

 rudimentary ; parasitic on the skin of Cetacea. 



Tribe 2. Crevettina. 



Ampldpoda with small head, small eyes, and midtiarticulate pediform 

 maxillipeds. 



Both pairs of antennae are long and multiarticulate ; in the male 

 they are larger than in the female. The upper or anterior antenna 

 are usually, as in Gammarus, the longer \ their shaft is composed of 

 several joints and bears a small accessory flagellum as well as the 

 principal one. The contrary may, however, occur, as in Corophium, 

 where the posterior antennae are elongated and pediform. The 

 maxillipeds in all cases fuse together at their base and form a large 

 under-lip, usually with four lamellae and two jointed pediform palps. 

 The coxal joints of the thoracic legs have the form of broad and 

 large epimeral plates. The abdomen has always the full number of 

 segments. The three posterior pairs of abdominal feet (uropoda) 

 are well developed and often much elongated. This group, which 

 includes an astonishing variety of forms, is principally distributed in 

 the colder seas. 



Fam. Corophiidae. The body is not laterally compressed. The posterior 

 antennas are more or less pediform. The coxal joints of the legs are frequently 

 very small They move rather by walking. Corophium lon<]icorne Fabr., dig 



