258 BULLETIN 15 8, UNITED STATES NATIONAL MUSEUM 



segment much swollen and trapezoidal in outline, the sixth segment 

 also swollen, the seventh and eighth tapered. The aesthetask is on 

 the fifth segment, is much widened, and is bent near its center. In 

 the first legs the endopod is about twice the length of the exopod and 

 its basal segment is five times as long as the end segment ; the latter 

 is invaginate on its inner margin and carries two unequal apical 

 claws. The exopod is fused into a single segment, but its component 

 parts are not indicated as clearly as in the female. The other three 

 pairs of legs show no sexual modifications; the fifth legs are also 

 very similar to those of the female, the distal segment not as strongly 

 narrowed at its base and its terminal spine much stouter. Total 

 length, 0.25-0.35 mm. 



Remarks. — This copepod is the smallest adult found within the 

 present area, and can be further identified by the first antennae, the 

 caudal rami, and the first legs. It swims very feebly, but crawls 

 about among the sand grains with considerable agility. 



QUINTANUS, new genus 



Body slightly depressed ; head fused with the first segment, a little 

 more than half the length of the rest of the metasome, and the 

 widest part of the body; second segment longer than either of the 

 three following segments, and slightly narrower than the head, the 

 rest of the body tapered regularly backward. Urosome only two- 

 fifths of the length of t;he metasome ; genital segment divided ; anal 

 segment longer than the penultimate segment ; caudal rami short and 

 wide, their apical setae very short. First antennae 6-segmented, 

 swollen, and geniculate in male ; endopod of second antennae 2-seg- 

 mented, tipped with two laminate setae, exopod 1-segmented. Exo- 

 pods of first four pairs of legs 3-segmented, endopods 2-segmented, 

 distal segment much longer than basal, setae on all the rami reduced 

 in number; fifth legs 2-segmented, but the segments completely 

 fused in both sexes. A single ovisac. 



Genotype. — Quintanus tenellus, new species. 



QUINTANUS TENELLUS, new species 



Plate 12 



Occurrence. — Twenty-five specimens, including both sexes, were 

 washed from the sand of Buzzards Bay bathing beach at Woods 

 Hole, July, 1927. The male holotype is U.S.N.M. No. 63431. 



Color. — Body transparent, with a decided whitish tinge but with- 

 out pigment markings ; eggs bluish ; no eye visible. 



Female. — Cephalic segment rather squarely truncated anteriorly 

 and narrowed posteriorly where it joins the second segment; rostrum 

 a mere knob, invisible in dorsal view ; fifth segment with a small 

 spine at each posterior corner; anal segment broadly romided pos- 

 teriorly, without a central incision. Caudal rami as wide as long, 



