BRITISH GENERA OF CLADOCERA 



51 



Summary of Characters of the British Genera.^ 



Tribe I. Calyptomera, Sars. — The post-cephalic 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 biranious in both sexes. Sida, 



Strans (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 jaroximal joint of the dorsal 

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

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



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

 rudimentary second ramus in the male. Holopedimn, Zaddach. 



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

 (Anomopoda). 



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

 ramus with four. 



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

 the foui'th and fifth pairs. The stomach with two forwardly -directed 

 diverticula. 



i. First antennae of female short. 



a A median dorsal spine on jjosterior margin of carapace. 

 Daphma, 0. F. ]\Iuller (Fig. 19) : first antennae of female 

 not mobile. The head sejmrated from tlie thorax only by 



Fam. 



Fam, 



Fi(i. 19. — Daphnia 

 obtusu, male, x 

 about 50. Oxford. 

 .1.1, Fh-st an- 

 tenna ; TVi. 1, first 

 tlioracic append- 

 age. 



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

 rhomboid jjattern. Ceriodaphnia, Dana : first antennae of 



' Consult Lilljeborg, Nov. Acta Itey. Hoc. Upsalensis, 1901 ; Scourfield, J. 



Quekett Mkr. Club, 1903-4. 



