North American Species of Diaptomus. 181 



width ; delicately hairy hoth within and without ; apex 

 bluntly rounded and armed with two spines, the inner long, 

 sharp, sinuously curved, the outer also sharply pointed hut 

 oiily ahout half as long as the inner. 



Length of female, 1.37 mm. ; of male, 1.28-1.68 mm. 



Found (not very abundantly) in material from West Oko- 

 boji Lake, Iowa, very kindly loaned me by Prof. L. S. Boss, 

 of Drake University, Des Moines, Iowa. 



This species is very similar to Dr. Forbes's D. piscina and 

 D. leptepus, but the details of structure will serve at once to 

 distinguish it from them. The hook on the first segment of 

 the right fifth foot of the male is very characteristic, as are 

 also the processes on the inner margin of the second basal 

 segment of the same leg. 1>. clavipes offers such a mass of 

 peculiar details that it is distinguished with ease from all 

 other species heretofore described. 



The name clavipes was chosen because of the club-like 

 inner rami of the fifth pair of legs of the male, the inner ramus 

 of the left leg especially resembling an Indian war- club. 



A very curious fact in regard to the distribution of this 

 species was noted. East and West Okoboji lakes are united 

 by a very deep, somewhat narrowed channel, but are so nearly 

 one lake that no account of the division is taken by Rand & 

 McNally in their atlas. Although there is nothing whatever 

 to hinder free migration from one part of the lake to the 

 other, not an individual was found in material from E. 

 Okoboji, taken the same day and under the same circum- 

 stances as that from W. Okoboji in which the specimens 

 were found. 



SPECIES INSUFFICIENTLY DESCRIBED. 



Diaptomus caroli Heerick. 



Diaptomus caroli, Ilerriek and Turner, '95, p. 69. 



This species name occurs once in the description of I), sici- 

 loides (Herrick and Turner '95), but although I have searched 

 diligently in Herrick's writings for an original description or 

 even a previous reference to this species, I have been unable 



