296 Birge — Notes on Cladocera. 



Schoedleri, Sars. It is not improbable, however, that both spe- 

 cies are varieties of the same form. The figures show, besides 

 the head of the male, the post abdomen and caudal claw of the 

 female, and two characteristic types of outline of the head of 

 the female. 



Daphnia Kahlbergjensis Schdl., var. breviceps, var. nov. 

 Plate XI, Figs. 1, 2, 3, 6. 



Female. — The animal is hyaline and the macula nigra is want- 

 ing. The species thus belongs to the section Hyalodaphnia of 

 Schoedler. The head is small, rounded in front and has a nar- 

 row crest. The rostrum is small, but always projects beyond 

 the sense-hairs. The valves are broadly oval in form and are 

 faintly recticulated. The spine is slender and of moderate 

 length. The first and second abdominal processes touch and 

 are slightly united at the base. The post abdomen has the 

 form characteristic of the section Hyalodaphnia. It bears 9-10 

 anal teeth, which are recurved and decrease in size from the 

 posterior end of the row. The caudal claws are provided with 

 the usual two teeth on their anterior (ventral) margin. They 

 have a pecten of fine teeth at the base, extending a little way 

 upon the claw. This is immediately followed by a second pec- 

 ten of 10-12 coarser teeth, which are longest in the middle. 

 Very fine denticles extend to the end of the claw. 



Length, 1.4 mm., including spine pf 0.3 mm., height, 0.7 mm. 



The male was not found. 



The length of the head is variable, but may be a little more 

 than one-fourth of the valves. Its anterior margin varies from 

 a form evenly rounded to one extending into a blunt point, as 

 is shown in the figures. The ventral margin of the head varies 

 from nearly straight to markedly concave, and the rostrum may 

 be merely a blunt, rounded termination or may be drawn out 

 into a well defined pointed, projection. The antennae are slender 

 and rather weak, not unusually long. When turned back the 

 ends of the setae do not reach the hinder margin of the valves. 

 The basal joint of the antennae extends beyond the anterior 

 margin of the head in some individuals and in others falls short 



