Marsh — North American Species of Dia'ptomus. 425 



as long as wide. The hook of the second segment is moderately 

 curved, and finely denticulate on the inner margin. The third 

 segment is represented by two spines, of which the inner is the 

 longer. The endopodite is slender, slightly exceeding in length 

 the first segment of the exopodite. It is setose at tip and hears 

 two rather long terminal spines. It is commonly composed of 

 one segment, but sometimes has two. 



The male fifth feet are of moderate length. The spines of 

 the first basal segments are slender and rather long. The sec- 

 ond basal segment of the right foot is longer than wide, and its 

 inner and outer margins are convex. The lateral hair is short, 

 and situated at the beginning of the distal fourth. The first 

 segment of the exopodite is as long as broad, and somewhat pro- 

 duced at the distal outer angle. From the posterior surface 

 near the internal distal angle extends a hyaline lamella. The 

 second segment is more than twice as long as its width, is 

 strongly convex on the outer margin, and slightly concave on 

 the inner. The distal end is about one-half as wide as the 

 proximal. The lateral spine is slightly curved, about half as 

 long as the segment and situated near the beginning of the 

 distal third. The terminal hook is slender, falciform, sym- 

 metrically curved, somewhat less in length than the rest of the 

 right foot. The endopodite is slender, either one- or two-seg- 

 mented, and considerably longer than the first segment of the 

 exopodite. The second basal seg-ment of the left foot is quad- 

 rate, slightly longer than broad, with the lateral hair situated 

 at the beginning of the distal fourth. The first segment ■ 

 exopodite is longer than wide, its inner surface strongly curved 

 and setose. The second segment is twice as long as wide. The 

 inner margin has two setose convexities, the distal one being 

 continuous with the rounded end of the segment. This segment 

 is terminated by two finger-like processes, the inner being shorter 

 and more slender. The left foot reaches to about the middle 

 of the second segment of the right exopodite. The endopodite 

 is long and slender, reaching about two-thirds the length of the 

 second segment of the exopodite. It is composed of either one 

 or two segiiient.s, and is setose at the tip. 



