2 PROCEEDINGS OF THE NATIONAL MUSEUM vol.73 



outer ramus very narrow, generally three articulations, middle joint 

 quite short and, in some instances, imperfectly defined. Oral parts 

 normal. First pair of legs with both rami triarticulate, the outer 

 one much shorter than the inner, and in some cases resembling, in 

 structure, that of the genus Dactylopusia; inner ramus with the first 

 joint slender and elongated, setae of inner edge attached close to the 

 end. Inner ramus of second pair of legs in male conspicuously trans- 

 formed, outer two joints confluent. Last pair of legs foliaceous, with 

 the proximal joint expanded inside; those in the male much smaller 

 than in the female. 



AMPHIASCUS COMMENSALIS, new species 



Specific characters — Adult male (Holotype, Cat. No. 61141, 

 U.S.N.M.) — Body proportion about the same as the female; male 

 shorter than the female. First antenna slightly longer than that of 

 female, first joint as long as fourth, second longer than third but 

 shorter than first, terminal portion a little more than one-half the 

 length of the posterior portion. Inner ramus of second pair of legs 

 transformed in the usual manner. Inner ramus of second pair longer 

 than the outer, distal joint produced at the end to a strong mucro- 

 niform projection. Last pair of legs much smaller than in the female, 

 with only two setae on the inner expansion of the proximal joint. 

 Distal joint oval, nearly circular in form, provided with five setae of 

 irregular length. The body has a yellowish color. 



Adult female. — Body moderately slender, with the posterior divi- 

 sions slightly narrower than anterior. Cephalic segment practically 

 as long as the four succeeding segments combined. Epimeral parts 

 evenly rounded in front. Rostrum prominent and lanceolate. Uro- 

 some about the length of the anterior division and tapering slightly 

 behind. Last segment corresponding approximately in length to 

 the preceding one. Furcal rami shorter than the anal segment, 

 outer and inner apical setae short. Anterior antennae comparatively 

 short and tapered distally, first joint much the longest, third joint 

 slightly longer than the second, and fourth longer than the third, 

 terminal portion about one-half the length of the posterior portion. 

 First pair of legs rather slender, outer ramus as long as the first joint 

 of the inner, all three joints of outer ramus approximately equal in 

 length, terminal joint with two clawlike spines and joints about 

 one-half as long as proximal joint. Last pair of legs with the distal 

 joint not long, oval in form, carrying five unequal setae, inner expan- 

 sion of proximal joint comparatively short, marginal setae, five, the 

 the middle one being the longest. Ovisac extending slightly beyond 

 the center of the urosome. 



Total length of female, 0.74 millimeter. Length of anterior body, 

 0.38 millimeter. Mean width of anterior portion, 0.18 millimeter. 



