parasitic on an Octopus. 473 



tliese proved to be minute copepod^, attached by their mouth- 

 appeudages to the skin o£ the octopu.^, their tail-ends being 

 tree. All tiie specimens found were females, most of them 

 with egg-sac-<. Tiiey appear to belong- to a new genus of the 

 llarpacticoidea, most nearly allied to tlie genus Idi/a, but 

 greatly modified for a parasitic life. It may, perhaps, be 

 held that a new family should be made for the genus, but 

 as all the appendages which have not undergone degeneration 

 liave retained, to a greater or less degree, their Id//a-\[ke 

 form, I have jjlaced it in the same family as Id>/a. 



The genus and species may be described as fallows : — 



Family Idyidae. 



Genus CuOLiDYA, nov. 



An Idyoid, modified for a parasitic life, in which the 

 swimming appendages are reduced or absent and thecephalou 

 and tjjorax soft and swollen. Cephalic appendages with the 

 same general structure as in the rest of the family. Inner 

 ramus of the second antenna very small. Mandible with 

 an unbranched palp. First maxilla forming a simple piercer. 

 First foot reduced in size, but of the same form as in the 

 genus Idi/a. Second foot two-branched, but with its jaunts 

 and setie reduced. Third and fourth feet absent. Fiftli feet 

 highly chitinized and ventral in position, connected by a 

 chitinized ventral plate. Abdomen not chitinized and with 

 feebly marked segmentation. Egg-sac one, attached. 



Cholidy a polypi, sj). n. 



Female (fig. 1) length 'ZS-'S mm. Cephalon slightly 

 flattened. 'J horax globular, swollen, filled with what appears 

 to be undifferentiated food or yolk-material. Abdomen 

 tapering from the swollen thoiax to the small furca. 



First antenna (fig. 2) six-jointed, the fourth joint bearing 

 a short pestiietask ; proportional length of joints, measured 

 along the upjK-r margin : — 



1 2 3 4 5 6 



10 23 12 8 7 7 



Second antenna (fig. 3) with two basal joints; cndopodite 

 very small, with two terminal setas ; exopodite tW(j-joint(id, 

 second joint about half as long as the first and bearing one 

 lateral and fuur terminal setse. 



