ENTOMOSTRACA OF MINNESOTA. 119 



ments of a rather small specimen: First segment of cephalothorax 

 0.24, second segment 0.068, third segment 0.06, fourth segment 0.036 

 mm.; the remainder of the body to the stylets measures 0.24 mm.,^ 

 while the stylets themselves are 0.021 mm. long and bear a lateral 

 spine about one-third their length from the apex. The longest seta is 

 0.24 mm. long, the outer median seta being about 0.19 mm. The body 

 is comparatively rather slender and tapering, with an unusually long 

 first thoracic segment. (Measurements of a large specimen of this 

 species may serve to indicate the observed fluctuation in size: Length 

 0.81 mm., thorax 0.50, abdomen 0.31, stylets 0.06, longest seta 0.40, 

 outer median seta 0.36 mm.) The antennte are considerably shorter 

 than the first thoracic segment, being about 0.19 mm. long, the sev- 

 enth and eighth joints about equal and the longest of the eleven seg- 

 ments. The first joint is very large. The antennne in a state of rest 

 assume a curved position. The antennules are small, the terminal 

 segment measuring (in the animal first above referred to) 0.032 mm. 

 The labrum has six similar teeth, which are bordered on either side 

 by a larger one. The longest joint of the outer maxilliped measures 

 0.06 mm. All the feet are usually two-jointed in both rami. The 

 outer ramus of the first pair of feet has the terminal joint armed exter- 

 nally with three stout spines, terminally with two setaj, and internally 

 with three setxe. The second and third pairs of feet are alike in their 

 spinous armature, the outer side of the terminal segment bearing 

 three spines, the end a very large toothed spine and a seta, and the 

 inside four sette. The fourth foot has two spines on the outside of the 

 terminal joint, a heavy spine and a seta terminally, and four setoe 

 within, while the terminal joint of the inner ramus bears externally 

 one spine, apically two spines, and internally three setse. The fifth 

 foot consists of a fleshy basal segment, more or less coalescent with 

 the last thoracic segment and bearing a curved spine externally, and 

 a terete terminal segment 0.012 mm. long, which has an apical seta 

 four times its own length. The abdomen is slender and its last seg- 

 ment bears a series of spines dorsally on the caudal margin. The egg- 

 sacs are appressed and contain eight to twenty rather large ova. The 

 color is bronzy and opaque. 



Although Marsh says his "specimens agree very well with the 

 descriptions of Sars and Schmeil, the only marked difference being in 

 the length of the caudal setse," we find several points of divergence 

 which may make it necessary to create a new variety or species. The 

 stylets are much shorter in the American form and the setae are 

 longer. The external apical seta is a well formed spine. The form of 

 the basal segment of the fifth foot is more as in C. varicans. there being 

 a decided protuberance to receive the second joint. The receptacu 



