188 BULLETIN 15 8, UNITED STATES NATIONAL MUSEUM 



First legs with 2-segmented rami, both tipped with claws; thf. 

 three succeeding pairs stout, with 3-segmented rami; fifth legs ex- 

 tended laterally, 2-segmented, the inner expansion of the basal seg- 

 ment narrow in the female, but fused across the midline in the male. 

 A single ovisac, large and considerably flattened. 



Genotype. — Zausodes arenicolus^ new species, 



Reiriarhs. — This genus resembles in many particulars the one estab- 

 lished by Goodsir in 1845 and called Zaus. But the fifth segment is 

 only a little narrower than the fourth and carries well-developed 

 e2)imeral plates, there is no trace of the dense ciliation on any of the 

 appendages, and there are so many structural differences in the 

 mouth parts, especially the maxillipeds, that it must be separated 

 and established as a new genus. Only a single species has been found 

 within the present area, but others will probably appear as the beach 

 sands are more carefully examined. 



ZAUSODES ARENICOLUS, new species 

 Plate 3 



Occurrence. — About 200 specimens, including both sexes and de- 

 velopment stages, were washed from the sand on the shore of Katama 

 Bay, Marthas Vineyard, August 5, 1927 (male holotype, U.S.N.M. 

 No. 63423). A few were also obtained from the sand of the southern 

 beach of Marthas Vineyard, beneath the Atlantic surf. 



Color. — Body semitransparent and without pigment markings; 

 eggs bluish, sometimes inclined to brownish; no eye visible. 



Female. — Metasome about the same width throughout, the lateral 

 epimeral plates with sharp posterior corners; fifth segment a little 

 reduced in length and width, its epimeral plates with bluntly rounded 

 corners. Urosome one-third as long as metasome, its epimeral plates 

 much reduced and inconspicuous ; caudal rami as wide as long, their 

 bases covered by the dorsal plate of the anal segment, their apical 

 setae comparatively short, the inner one about twice the length of 

 the outer; anal segment twice the length of the penultimate segment, 

 with rounded posterior corners. Rostrum large, broadly rounded at 

 the tip and well defined at the base. First antennae slender, the 

 four basal segments fairly long, the four terminal ones very 

 short, all well armed with setae, and the fourth segment carrying 

 an aesthetask twice the length of the terminal portion of the an- 

 tenna. Second antenna with its proximal segment distinctly divided 

 and much longer than the distal segment; the latter is tipped with 

 three long geniculate setae about equal in length, and has two or 

 three small spines on its inner margin, and a small spine and a short 



