EDRIOPHTHA LMIA . 



73 



feet varies from five to seven, and the branchial sacs are attached to the first four 



segments, or to only one or two of them. 



The Capeellidje are long and slender forms, with well-devel- 

 oped antennas and antennulse. They live in salt-water, walking 

 around on submarine plants in a very deliberate manner, and 

 progress by a doubling-up of the body in about the same way 

 that the measuring worm does, and the most common specie^ 

 on the Atlantic coast, received its name (^Caprella geometrica) 

 from this habit. 



The other family of this sub-order has re- 

 ceived the name Cyamid^e, from its leading 

 genus, Cyamus. These are the whale-lice 

 which live attached to the skin of whales. 

 Each species of these marine mammals prob- 

 ably has its own species of parasite. They 

 are small forms, a quarter or a half an inch 

 in length, with rudimentary antennae, five 



Fio ofi rn.r.iin n.n. P^^'^ "^ ^^^^^ ^""^ ^^^ P^^''^ "^ brauchial sacs ^^g^So";isef eSrged!' 



metrica on a branch attached to the third and fourth segments 



yzoa. ^j ^-^^ body. The size of these sacs exhibits much variation; in 



C. ceti they equal the longest of the limbs in length; in other forms they are pro- 

 portionately much shorter. 



Sub-Oedbk II. — Amphipoda Genxjina. 



This group contains the numerous forms in which the head is clearly distinct from 

 the first thoracic segment, and which have the abdomen well developed, and composed 

 of from five to seven segments, most of which bear appendages. 



Our first family, Oxycephalidje, embraces a few long and slender forms found on 

 the high seas. The head is greatly elongate, and the feet do not have the basal joint 

 expanded. The peculiar features acquire their greatest development in Rhabdosoma, 



Fig. 98. — Bhabdosama batei, enlarged. 



of which we figure a species from the middle of the Pacific ocean. None have been 

 recorded from either coast of the United States. These forms swim by doubling the 

 , body, and then suddenly extending it. 



In the family Pheonimid^ the antennae are absent, at least in one sex ; while the 

 antennulae are well developed, the maxilla are more or less rudimentary. Phronima, 

 the typical genus, is a sort of hermit among the Amphipoda ; for it lives in the dead 

 tubes of JBeroe, Pyrosoma, and other similar pelagic forms. A species occurs in our 

 waters. Near Phronima and Ilyperia is to be placed the large Amphipod, Thau- 

 mops pellucida, which was taken by the " Challenger " expedition off Gibraltar, at a 

 depth of nearly twelve hundred fathoms. It is perfectly transparent, and receives its 



