COPEPODA FROM IFALUK ATOLL 29 



Segment 2 of endopodite leg 1 with 2 internal setae; segment 3 with a total 

 of 6 setae Pseudocyclopina Lang 



12. 2nd segment of endopodite leg 1 with 2 setae . Cyclopinodes C. B. Wilson 

 2nd segment of endopodite leg 1 with 1 seta 13 



13. Body elongate, cephalothorax merging almost imperceptibly into abdomen. 



Metacyclopina Lindberg 

 Cephalothorax and body distinctly separate 14 



14. Mandibular exopodite reduced, represented by 1 seta. Some setae of the 



3rd segment of legs 1 to 3 replaced by spines, antennules 12-segmented. 



Cyclopinella G. O. Sars 

 Mandibular exopodite 4-segmented, not reduced. 3rd segment of endopo- 

 dite legs 1 to 3 with normally developed setae, antennules 18-19-seg- 

 mented Cyclopinoides Lindberg 



Genus Cyclopina Glaus, 1863 



In addition to the structure of the oral appendages and the setal 

 and spinal formulae of the legs, the distinctions among the many- 

 species of this genus are based to a large degree upon such character- 

 istics as the development of the spines on the terminal segment of 

 leg 5, the shape of that segment, the length of the furcal rami, and 

 the place of insertion and development of the marginal setae. Very- 

 likely this group of characters is subjected to a certain amount of 

 variation, as appears from the inspection of a group of representatives 

 of one of the more common forms. The total body length, as well 

 as the proportional lengths of cephalothorax and abdomen, may be 

 variable from natural courses or may be influenced by contraction of 

 somites as a result of fixation. It seems very possible, therefore, 

 that the number of species will be reduced when more specimens, es- 

 pecially of the less common forms, become available. The following 

 key, adapted from Lindberg (1953), may serve to distinguish the 

 females of Cyclopina; its value is limited and comparison with re- 

 liable descriptions remains a very necessary check. 



Key to the Females of Cyclopina 



1. Furcal rami about as long as broad or broader than long 2 



Furcal rami distinctly longer than broad 4 



2. Internal spine of terminal segment of leg 5 with lamelliform edges, ovate; 



no spinule at the base of the external spine on that segment. 



C. schneideri T. Scott 



Internal spine on terminal segment of leg 5 without lamelliform edges, 



slender; a small spinule at the base of the external spine on that segment. 



3 



3. External spine on terminal segment of leg 5 short, about as long as apical 



segment. Apical segment of mandibular exopodite with 2 setae, one of 

 which is considerably lengthened and slightly swollen, bearing a tuft of 



hairs at the apex C. laurentica Nicholls 



External spine of terminal segment of leg 5 long and slender, more than 1% 

 times as long as terminal segment. Condition of mandibular exopodite 

 unknown C. heterospina Shen and Bai 



