North American Species of Didptomus. 155 



" The inner margin of the first segment of the outer ramus 

 of the right fifth foot of the male dilated into a rather large 

 hyaline lamella. The second segment of this ramus moder- 

 ately curved, the outer margin ohtusely biangulate, the spine 

 placed below the middle. Claw simply curved. Inner ramus 

 small and slightly surpassing the middle of the first segment 

 of the outer ramus. 



" The second segment of the outer ramus of the left fifth 

 foot almost triangular, with a beak-like spine and delicately 

 hairy within (intus tenai ore et subtiliter hispido); the apical 

 process obtuse, with a spine at the inner margin. Inner 

 ramus simple, sinuous, and reaching to or beyond the middle 

 of the second segment of the outer ramus. 



"Length of female about 1.3 mm.; that of male slightly 

 less. 



" Found in the month of May in Lake Tulare near the city 

 of Fresno, Cal., by G. Eisen. 



"In the general form of the body this Diaptomus closely 

 resembles D, gracilis Sars as well as D. sicilis Forbes. It is 

 on account of this last resemblance that it was called siciloides. 

 It differs, however, from both : from D. gracilis in the shape of 

 the last thoracic segment and of the abdominal segments, of 

 the first pair of antennae, and of the fifth pair of feet ; from D. 

 sicilis in the shape of the fifth pair of feet, although this dif- 

 ference is not very great. It resembles D. sicilis more closely 

 than D. gracilis. 



"It seems to live in great numbers in Lake Tulare near 

 Fresno, Cal. The female bears only four eggs."* 



The statement concerning the number of eggs borne by the 

 female is erroneous, the number being variable, and appar- 

 ently dependent to a great degree on the temperature of the 

 water and on the food supply. In the high mountain lakes 

 from which the species was first described the statement 

 above quoted may hold true, but in the warm sluggish waters 

 of the Illinois Eiver, where food is abundant, the egg-sac is 

 very large, as many as eighteen eggs having been counted 

 on a single female. This is true also of specimens taken 



*Lilljeborg*s description from de Guerne et Richard, 89b. 



