COPEPODA FROM IFALUK ATOLL 141 



have drawn attention already to the fact that the hyahne lamella on 

 the 2 internal setae is overlooked very easily, which seems the more 

 likely in A. Scott's figure since he probably made his drawings from an 

 unstained specimen. There is also a slight difference in the structure 

 of leg 5; in Scott's specimen the two fine apical setae of the exopodite 

 appear to have been of equal length ; here they are distinctly unequal. 

 P. exUjuum originally was described from a single female specimen 

 found in washings of marine invertebrates dredged at a depth of 

 13 meters off Pulu Jedan in the Aru Islands by the Siboga Expedition. 

 The present specimens are from sand samples taken some 40 feet 

 from the reef margin at Falarik in the Ifaluk Atoll. 



Family Thalestridae G. O. Sars, 1905 



In the discussion of the Ifaluk representatives of this family I will 

 base myself on Lang's monograph for reasons of stability. The divi- 

 sion of such a large family always will depend largely upon the 

 personal opinion of the investigator concerned. Lang's division, 

 which is repeated below with the new genera described, seems quite 

 sound though, unfortunately, the reasons for substitution of a new 

 name, etc., cannot always be lifted distinctly from the lengthy dis- 

 cussions. At Lang's suggestion the family is split into four sub- 

 families. 



Subfamily Thalestrinae G. O. Sars, 1905: Genera Thalestris Glaus, 



1863 (type species T. longimana Claus, 1863), Amenophia Boeck, 



1864 (type species A. peltata Boeck, 1864), Parathalestris Brady and 

 Robertson, 1873 (type species Thalestris clausii Norman, 1868), and 

 Phyllothalestris G. O. Sars, 1905 (type species Thalestris mysis Claus, 

 1863). 



Subfamily Rhynchothalestrinae Lang, 1948: genera Rhynchothales- 

 tris G. O. Sars, 1905 (type species Thalestris rufocincta Brady, 1880), 

 and Pelthestris (type species P. tripartita Monard, 1924). 



Subfamily Dactylopusinae Lang, 1 936 : genera Diarthrodes Thomson, 

 1882 (type species D. novae zealandiae Thomson, 1882), Eudactylopus 

 A. Scott, 1909 (type species Dactylopus latipes T. Scott, 1894=£'. 

 andrewi Sewell 1940), Dactylopodopsis G. O. Sars, 1911 (type species 

 D. dilatata G. O. Sars, 1911), Dactylopusioides Brian, 1928 (type 

 species Dactylopus macrolahris Claus, \S^^= Dactylopusioides stamp- 

 aliae Brian, 1928), Dactylopusia Norman, 1903 (type species Dactylopus 

 tishoides Claus, 1863), Paradactylopodia Lang, 1948 (type Dactylopus 

 latipes Boeck, 1864), Neodactylopus NichoUs, 1945 (type species 

 N. cyclopoides NichoUs, 1945), and Diarthrodella Klie, 1949 (type 

 species D. orbiculata Klie, 1949). 



Subfamily Pseudotachidiinae Lang, 1936: genera Idomene Philippi, 

 1843 (type species /. Jorjicata Philippi, 1843), Pseudotachidius T. 



