204 Field Columbian Museum — Zoology, Vol. VIL 



in the collections from Lakes Atitlan and Amatitlan. Length 

 i.o mm.; height to 0.45 mm. 



Family Daphiiiclse. 



Daphnia pulex De Geer. 



By far the most abundant member of the Cladocera in the 

 collection is a stout, semi-transparent representative of this 

 species. The antennae are not very strong, and only slightly 

 ciliated. The first and second abdominal processes are united 

 at the base. There are 17-18 abdominal teeth. The distal 

 pecten bears 6-8 teeth, of which the proximal is smaller than the 

 others. The proximal pecten has about 10 small teeth. Length 

 to 2 . 5 mm. ; height to i . 6 mm. Lakes Atitlan and Amatitlan. 



Daphnia longispina O. F. Muller. 



A single specimen of this species was found in the collections 

 from Lake Amatitlan. It is of the variety galeata Sars, and is 

 not far from the form figured in Lilljeborg's Cladocera SuecuB, 

 PI. XVII, fig. 9. Length 1.56 mm., including spine 0.4 mm. 

 long; height 0.53 mm. 



Ceriodaphnia rigaudi Richard. 



Four immature specimens of this species were found in the 

 collection from Lake Amatitlan. They included both varieties, 

 three having one horn, and one specimen having two horns on the 

 head. Length 0.4 mm. 



Family BoMiiiiiiidw. 



Bosmina obtusirostris G. O. Sars. 



A few specimens indistinguishable from this species were 

 found in both lakes. Length 0.42 mm. 



Family li,vii<*«»ldn'. 



Alona, s]). 



Two immature specimens of a species of this genus were 

 found in the collection from Lake Atitlan. Length 0.3 mm. 



