Marsh — North American Species of Diaptomus. 415 



In the fifth feet of the male the spines of the first basal seg- 

 ment are rather large. The second basal segment of the right 

 foot is broader than long and much swollen on the inner side. 

 The lateral hair is at the beginning of the distal third. The 

 first segment of the exopodite is trapezoidal, and as broad as 

 long. The second segment is stout, its length exceeding its 

 breadth by about one-half. At the middle of its inner margin 

 is a small spine. Tlie lateral spine is of moderate length, nearly 

 straight, and denticulate on the inner margin. It is situated 

 at the distal angle of the segment. The terminal hook has the 

 symmetry of the curve broken by two rather abrupt angles; 

 its inner margin is finely denticulate. The endopodite is stout 

 and somewhat spindle-shaped. It is attached to the side of the 

 second basal segment. It is setose at the tip, and reaches nearly 

 to the middle of the second segment of the exopodite. The sec- 

 ond basal segment of the left fifth foot is quadrate and nearly 

 equal in length to the corresponding segment of the right foot. 

 The lateral hair is situated well towards the distal end of the 

 segment. The first segment of the exopodite is trapezoidal, the 

 distal end being very narrow. The second segment consists 

 of an oval base and two elongated digitiform processes. The 

 basal part is setose on the inner margin. Of the terminal proc- 

 esses, the posterior one is ihe longer. The anterior one is 

 enlarged and denticulate at tip and is separated from the seg- 

 ment bv a distinct joint. The endopodite is one-segmented and 

 nearly equal in leng*th to the exopodite. The whole foot reaches 

 to the middle of the second segment of the exopodite of the right 

 foot. 



Length of female, 1.2 mm. Length of male, 1.1 mm. 



The original description was from material sent by Professor 

 Birge and obtained in Jackson, Mississippi. I have since found 

 it in collections made by Professor Birge in Guzman and Sli- 

 dell, Louisiana, and Schacht reports it from lakes in Florida. 



