EDRIOPHTHALMIA . 



73 



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

 segments, or to only one or two of them. 



The CAPKELLID^E are long and slender forms, with well-devel- 



oped antennae and antennulae. They live in salt-water, walkino- 



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 species 



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 antenna?, five 



P f ***** ^ tW P* f branchial S&CS 



metrica on a branch attached to the third and fourth segments 



of the 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. 



FIG. w.- 



g eo- 



SUB-ORDER II. AMPHIPODA GENUINA. 



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, OXYCEPHALID^E, 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. Rhabdosoma batel, 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 PHRONIMID^E the antennae are absent, at least in one sex ; while the 

 antennulae are well developed, the maxillae 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 Beroe, Pyrosoma, and other similar pelagic forms. A species occurs in our 

 waters. Near Phronima and Hyperia is to be placed the large Amphipod, JTtcm- 

 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 



