270 HISTORY OF BRITISH CRUSTACEA. 



of movement. Iu a vessel in which he kept some, he fre- 

 quently saw them turn head-over-heels, throwing a regular 

 summersault ten or a dozen times in succession. 



Daphnia vetula, M tiller, p. ; Baird. — Carapace ovate, 

 small, transparent ; striated hinder extremity without spine ; 

 head blunt, small, beak not very prominent. 



Hab. Ponds and ditches, in summer and autumn. 



Daphnia reticulata, Jurine, sp. — Carapace rounded- 

 oval, slightly greenish, surface covered with a complete 

 mesh- work of small hexagonal cells ; lower extremity with a 

 short spine ; head rather small, without beak ; sixth seg- 

 ment of body with a spur. 



Hab. Ponds and ditches, in summer and autumn. 



Daphnia rotunda, Strauss. — Carapace almost quite 

 round, lower extremity with a short blunt spine; colour 

 reddish ; sixth segment of body without a spur. 



Hab. Ponds and ditches near London. 



Daphnia mucronata, Muller. — Carapace with its front 

 edge quite straight, and ending below in a spine of some 

 length ; the whole creature is of a dark gray. 



Hab. Ponds about Isleworth. Dr. Baird found two 

 varieties there ; one has the head rounded above, the other 

 has the head ending in a sharp point directed upwards. 



