276 U.S. NATIONAL MUSEUM BULLETIN 23 6 



Leg 2 (fig. 1116) with 3-segmented exopodite and 2-segmented 

 endopodite. Legs 3 and 4 with 3-segmented endopodite and exopo- 

 dite. The various details of the legs can best be taken from figures 

 lllb-d; the setal formula is: 



endopodite exopodite 



leg 2 1.120 0.0.023 



leg 3 1.1.021 0.0.023 



leg 4 1.1.221 0.0.223 



No seta along internal border of 3rd exopodal segment of legs 

 2 and 3. Leg 4 with strongly developed exopodite; internal border of 

 segments 1 and 2 produced into fine tooth. Setae of endopodite 

 very fine. 



Leg 5 very small. Baso-endopodite scarcely elevated, reaching 

 % length of exopodite, with 2 setae. External lobe scarcely visible, 

 with very fine seta. Exopodite twice as long as wide, with 5 marginal 

 setae, distribution of which appears clearly from figure 111^. 



The specimen is completely colorless and almost transparent; no 

 eye or pigmented spots could be observed. 



Remarks. — This new species is, as appears from the segmentation 

 and setation of the endopodites, closely related to Leptomesochra 

 ajricana Kunz, 1951, but different in the size (it is only half as long), in 

 its smaller rostrum, and in details of the setation of legs 3, 4, and 5. 

 A single female specimen occurred in a sand sample taken some 340 

 feet from the reef margin at Falarik in the Ifaluk Atoll. 



Family Tetragonicepsidae Lang, 1944 



The genera Tetragoniceps Brady, 1880, Pteropsyllus T. Scott, 1906, 

 Diagoniceps Willey, 1930, and Phyllopodopsylhts T. Scott, 1906, were 

 independently brought to separate families by Lang (1944, p. 27) in 

 his family Tetragonicepsidae and by NichoUs (1944, p. 492) in his 

 family Pteropsyllidae. Lang's paper is dated February 10, 1944; 

 Nicholls', August, 1944; Lang's name clearly must have priority. 

 Lang also split up the genus Phyllopodopsyllus, viz, Phyllopodopsyllus 

 T. Scott, 1906, sensu Lang, with type species Tetragoniceps bradyi 

 T. Scott, 1892, and Paraphyllopodopsyllus, Lang, 1944, with the type 

 species Phyllopodopsyllus mossmani T. Scott, 1912. The genus 

 Phyllopodopsyllus in its restricted sense is represented in the Ifaluk 

 collection by one of its species. 



Genus Phyllopodopsyllus T. Scott, 1906 



The differences between Phyllopodopsyllus T. Scott and Paraphyl- 

 lopodopsyllus Lang, 1944, have become very vague since the introduc- 



