42 TWELFTH ANNUAL REPORT, 



clums\% and the continuation of the fornices runs toward the apex 

 of the incurved beak, which commonly lies within the valves of the 

 shell. The lower anterior angle has a prominence and there is a 

 basin-shaped area inclosing the base of the antennae, part of which 

 lies on the shell and part on the head. This area is more strongly 

 lined or reticulated than the rest of the shell. The lower margin 

 is straight and terminates, in most forms, in a long scythe-shaped 

 spine which is directed backward. The shell itself is usually indis- 

 tinctly reticulate or unmarked, and commonly is deep colored. The 

 pjst-abdomen is very like Ceriodaphniaor moreas in Simocephalus; 

 the anal spines are few and the older specimens have more than the 

 young; the place at which additional spines are to appear is^ 

 marked by prominences. The eye is of moderate size, the pig- 

 ment fleck rather small and the antennules short and hidden by the 

 beak. The antennae are of small size and generally dark colored. 

 The ephippium contains but one egg; the males do not have al- 

 tered antennae or feet. The sexual periods fall in early summer 

 and in autumn, according to Weismann; the males appear but 

 sparingly. The species S. mucronata is very abundant every- 

 where, while the others are less frequently seen. 



Sp. 1. Scaplioleberis iniicronata, Mueller. 

 (Plate J. Fig. 5.) 



Daphnia mucronata, Mueller, Leivin, Lilljeborg, f ischkk, Leydig, Baird, 



Herrick. 

 Scapholeberisrmteronata, SchOeuIjKR, P. E. Mueller, Kurz, WeiSMANN, Bikge, 



Herrick. 



This wel.'-known species with rather short spines below is found 

 abundantly everywhere. In this country at least it is character- 

 ized by a dark color. The head is large, rounded in front of the 

 large eye, serrate below and extending posteriorly into a roundish 

 beak, back of which are the short antennules. The fornices are 

 very short and rounded: a line connects the fornices with the beak 

 by a sudden deflection downward; it sets ofl'the area which forma 

 a part of the basin of the antennae. A second line springing from 

 just above the termination of the fornices passes over the eye by a 

 broad curve. The post-abdomen is truncate and bears beside the 

 terminal claws four or more spines which rapidly decrease in siz^». 

 The claws are minutely spined; the spines on the shell are of vari- 

 able length, but do not exceed one-fourth the length of the re- 

 mainder of the lower margin. This species ranges over all Europe 

 and eastern United States. 



Length 0.6 mm, — 0.8 mm. 



