132 TWELFTH ANNUAL REPORT. 



first and third joints, borne at the tips of long spines. The anteu- 

 nules are short, the ramus apparently but three-jointed, the short, 

 median joints common in this appendage being only obscurely in- 

 dicated. The mandible has but seven teeth, the first simple and 

 acute, separated from the second by an interval about equal to the 

 second and third, the second to the sixth bifid, the seventh entire 

 and acute. The usual plumose bristle is replaced by a sharp, 

 simple spine. 



The outer ramus of the fourth pair of legs has two teeth at the 

 outer tip of each of the two basal joints. The terminal joint of 

 this ramus is armed as follows: a short simple spine at middle of 

 outer margin and another at the distal outer angle; a single and 

 long terminal seta, strongly and sharply toothed externally and 

 plumose within, and four long plumose setge attached to the inner 

 margin. 



The left leg of the fifth pair in the male, viewed from behind, has 

 the basal joint very large, broader than long, with the inner inferior 

 angle produced downwards as a long, stout, curved process or arm 

 as long as the two remaining joints. The second joint is trapezoid- 

 al, shortest within. The third joint is about half as wide at base 

 as the first, is straight without, with a sharp, small tooth at its 

 distal third, and bifid at tip. On the inner margin this joint is at 

 first dilated a little, and then deeply' excavated to the narrow tip, 

 to receive the lower end of the left leg, the lower two-thirds of this 

 margin forming the segment of a circle. 



The right leg is two-jointed, the first joint twice as broad, enlarg- 

 ed at the lower end, forming an auriculate expansion at its inner 

 inferior angle. The second joint is conical in outline and about 

 two-thirds as long as the first. 



The terminal bristles of the rami are very broad and strong in the 

 female, the outer one especially having an extraordinary size and 

 thickness. There is also at the outer angle of each ramus a short, 

 stout spine, that on the left ramus being inflated like the outer 

 bristle. Length .065 in. 



The legs of the fifth pair in the female are three-jointed and 

 similar, the basal joint short and broad, the second two and one- 

 half times as long as wide. The leg terminates by four diverging 

 teeth, preceded by two others, one on each side. 



Taken in the towing net abundantly in October, 1S81, at Grand 

 Traverse bay; also obtained rarely by Mr. B. W. Thomas, from the 

 city water of Chicago." 



Occurring in Minnesota, probably in lake Superior. 



