1886.] PROCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 311 



^Tbis species is rather below the average size for the ^eniis, and in 

 shape and general appearance more closely resembles Pandarus bicolor, 

 of Europe, than any other described species. It may readily be distin- 

 guished from P. bicolor, however, by its smaller size, narrower frontal 

 plates, the much smaller dorsal lobe of the third ct'phalo-thoracic seg- 

 ment, and the smaller terminal caudal plate. T\\^^ swimming feet, and 

 especially those of the fourth pair, also present considerable differences. 



In dorsal view, the body is elongate-oval in outline, with the length 

 equal to about twice the greatest width, which is near the hinder end 

 of the anterior segment, or across the dorsal appendages of the second 

 segment. The anterior segment is moderately convex, (juite regularly 

 semi-elliptical in outline, and about three-sevenths as long as the entire 

 body; leugth to width about as 3 to 4^ or 5 to 6 ; anterior margin reg- 

 ularly rounded ; postero lateral angles more or less acute or slightly 

 rounded, moderately produced and frequently directed slightly inward. 

 The posterior margin, when perfect, bears three or four short, broad, 

 and sharply pointed teeth-like projections on each side of, and near to, 

 a rounded median one. More often all the projections are blunt and 

 rounded, and frequently the margin is more or less irregular and jagged, 

 •with a slight irregular notch near the middle, and has but few small, 

 ill-defined teeth, which are seldom regularly i)laced, there being often 

 but one or two on each side of the center. The frontal shields are of 

 medium width, with the anterior margin generallj' but slightly curved 

 along the middle, and the median notch of moderate size. They broaden 

 gradually to the point where they become free, beyond which they re- 

 tain a nearly uniform width, the outer extremities being more or less 

 regularly rounded. Sometimes they are broader and more curved on 

 the outer side, but in no case do they attain so great a width as in 

 Pandarus bicolor. 



The lateral dorsallobes of the second segment are oval in dorsal view, 

 and placed somewhat obliquely. The inner posterior margin generally 

 presents an outward curve, but is sometimes nearly straight or slightly 

 concave; the posterior extremity is well rounded. These lobes are 

 rather widely separated and overlap the appendage of the succeeding 

 segment but slightly, though projecting a short distance back of it, and 

 reaching about half way from the posterior margin of the first segment 

 to the posterior margin of the fourth segment. 



Dorsal appendage of the third segment comparatively small, about 

 twice as wide as long, and with a deep sinus in the middle, which 

 reaches about one-half its length, and partly separates it into two equal 

 and very regular lobes. At the margin the sinus opens broadly with 

 concave sides, but farther in its edges approach more or less closely to- 

 gether, and are nearly parallel. In advance of the sinus there is a 

 circular translucent area, which, under a low-power lens, appears to 

 be an extension of it, and to greatly increase its length and width as 

 shown on plate VI, fig. 1, 



