172 GEOL. AND NAT. HIST. SURVEY OF MINNESOTA. 



men is broad and obliquely traacate. The difference between being 

 obliquely truncate and narrowed at the end in some circumstances 

 disappears, so that really this species seems quite close to laticaudata. 

 Found in Madison, Wis. 



Ceriodaphiiia quadrang-ula Mueller. 



Plate XLI, Figs. 16-18. 



Daphnia quadrnngulo — O. F. Mueller. 

 Daphnia reticulata — Baird. 



Head depressed, rounded at the end, only slightly angled; fornices 

 prominent, antennules large; post-abdomen narrow, of equal width 

 for the lower half, rounded at the end, with about eight small spines; 

 claws smooth, length about 0.6 mm. This species resembles a smooth- 

 clawed D. reticulata. 



* Ceriodaphnia scitula Herrick. 

 Plates XLII, Figs. 5-8; XLIV, Figs. 1, 2; XLV, Fig. 1. 



One of the most abundant species of Ceriodaphnia in Minnesota is a 

 large form much resembling C. qiiadrangula. The post-abdomen is 

 exactly as in C. reticulata or G. dentata, which latter it resembles in 

 having a sharp angulation in front of the antennules. The shell is 

 oblong and heavily marked with minute, regular hexagonal lining; 

 the upper angle is rather sharp. The head is closely appressed, the 

 fornices are prominent and abruptly truncate at the tip, the eye is 

 small, the pigment fleck also small; antennules short. The post- 

 abdomen is of moderate size, narrowed toward the end and armed 

 with about ten powerful curved spines; the terminal claw itself is 

 large and curved, armed only with fine spines extending down the en- 

 tire inner side. The size is 0.8 to 1.0 mm.; color pinkish, opaque; 

 antennae, especially, often bright piok. Male 0.6 mm.; flagellum of 

 the male antennce long; sensory filaments lateral, also one anterior, 

 lateral flagellum. 



Distinguished from C. qiiadrangula by the prominent fornices, large 

 anal spines, small reticulations, form of head and larger size. 



A small variety resembling the above very closely is the common- 

 est form in our larger lakes; the reticulation is commonly larger but 

 less distinct, the head is depressed and narrowed, with a sinuous 

 upper outline. The fornices are prominent and the form of the post- 

 abdomen is exactly as in the last. The spines of the post-abdomen 

 are very long and seated on small eminences. The length hardly ex- 

 ceeds 0.55 mm. The claw is densely ciliated, but not spined; these 



