COPEPODS OF THE WOODS HOLE REGION 179 



ARENOSETELLA SPINICAUDA, new species 



Plate 2, or-l 



Occwrrence. — Fifty specimens, including both sexes, were washed 

 out of the sand on the Buzzards Bay bathing beach at Woods Hole 

 (male holotype, U.S.N.M. No. 63421) ; 10 females were washed out 

 of the sand on the shore of Cape Cod Bay at the Dennis bathing 

 beach; 2 females washed from the shore sands of Katama Bay, 

 Marthas Vineyard. 



Color. — Body transparent and colorless, without pigment mark- 

 ings. 



Female. — Body seven and one-half times as long as wide, slightly 

 tapered posteriorly; cephalothorax as long as the second and third 

 thoracic segments combined, scarcely narrowed anteriorly and not 

 vaulted dorsally ; urosome more than half the length of the metasome, 

 without spinules. Genital segment not divided, considerably longer 

 than the first abdominal segment; anal segment short, twice as wide 

 as long, with a pair of claws on its dorsal surface, close together, one 

 on either side of the midline near the posterior margin of the seg- 

 ment. The bases of the claws are separated by a short space, are 

 articulated to the surface of the segment, and the claws curve back- 

 ward over the caudal rami, just reaching the tips of the latter. The 

 caudal rami are as wide as long and quadrangular, the inner apical 

 seta longer than the urosome, the next seta half as long, and both of 

 these setae jointed near the base. 



The first antennae are very slender, and, if we include the terminal 

 aesthetask, are longer than the cephalic segment. The basal segment 

 is slightly enlarged and the rest of the antenna is turned outward 

 at an angle with it; the second and third segments are setose on the 

 anterior margin, the other segments only sparsely so; the second 

 segment carries an aesthetask, which reaches beyond the tip of the 

 antenna, and the end segment is tipped with another aesthetask, as 

 stout as the segment itself and as long as the whole antenna. 



The second antennae are exceptionally large and curl up over the 

 dorsal surface of the head; the endopod is 3-segmented, the middle 

 segment a little longer than either of the others, the terminal seg- 

 ment spatulate, with a pectinated spine on the inner margin, 4 stout 

 terminal spines, and a minute spinule on the outer margin. The inner 

 terminal spine is twice the diameter of the others and is jointed near 

 the middle ; all four of these spines are sparsely pectinated. The exo- 

 pod is 3-segmented, the end segment as long as the two basal seg- 

 ments combined and tipped with two unequal setae, with three short 

 hairlike setae in a transverse row across the center of the segment. 



The rami of the first four pairs of legs are very slender, the exo- 

 pods reaching the tip of the middle segment of the endopods and 



