BRITISH GENERA OF CLADOCERA 



SI 



Summary of Characters of the British Genera.^ 



Tribe I. Calyptomera, Sars. — The post-cephalio portion of the body 

 enveloped in a free fold or carapace. 



A. Six pairs of thoracic feet, the first pair not prehensile (Ctenopoda), 

 Fam. 1. Sididae : second antennae biramous in both sexes. Sida, 

 Straus (Fig. 11) : second antenna with three joints in the dorsal 

 ramus, two in the ventral ; the rostrum large, the teeth on the 

 telson many. Latona, Straus : second antenna with two joints in 

 the dorsal ramus, three in the ventral, the proximal joint of the dorsal 

 ramus provided with a setose appendage. Daphnella, Baird : second 

 antenna with the joints as in Latona, but ■\vith no setose appendage. 



2. Holopediidae : second antennae not biramous in the female ; a 

 rudimentary second ramus in the male. Holopedium, Zaddach. 



Four to five or six pairs of thoracic feet, the anterior pair prehensile 

 (Anomopoda). 



A. Ventral ramus of second antenna with three joints, the dorsal 

 ramus with four. 



3. Daphniidae : five pairs of thoracic feet, with a gap between 

 the fourth and fifth pairs. The stomach with two forwardly-directed 

 diverticula. 



i. First antennae of female short. 



a A median dorsal spine on posterior margin of carapace. 

 Daphnia, 0. F. Muller (Fig. 19) : first antennae of female 

 not mobile. The head separated from the tliorax only by 



Fam. 



B. 



Fam. 



Fig. 19. — Daphnia 

 obtusa, male, x 

 about 50. 0.\ford. 

 A.l, First an- 

 tenna ; I'h.l, lirst 

 thoracic append- 

 age. 



a slight constriction or not at all. Cuticle with a quadrate 

 rhomboid pattern. Geriodaphnia, Dana : first antennae of 



' Consult Lilljeborg, Nov. Ada Jieg. Soc. Upsalensis, 1901 ; Scourfield, /. 

 Quekett Micr. Club, 1903-4. 



