II FAMILIES OF CLADOCERA 53 
Fam. 4. Bosminidae: feet equidistant, five or six pairs; the first 
antennae of the female immobile, with sense-hairs arranged in rings, 
not forming an apical tuft. The intestine uncoiled ; no caeca. 
Bosmina, Baird (Fig. 22). 
Fam. 5. Lyncodaphniidae : four, five, or six pairs of equidistant thoracic 
limbs; the first two pairs prehensile. First antennae of female 
mobile, with apical sense-hairs. Intestine coiled or straight: 
i. Four pairs of thoracic limbs. Lathonwra, Lilljeborg. 
i. Five pairs of thoracic limbs. 
a. The four-jointed ramus of the second antenna with four 
swimming hairs. Macrothriz, Baird: the first antennae 
of the female flattened, curved. The intestine simple, 
straight. Streblocerus, Sars: first antennae of the female 
very little flattened, curved backwards and outwards. The 
intestine coiled, the stomach with two forwardly-directed 
caeca, 
b. The four-jointed ramus of the second antenna with only 
three swimming hairs. Drepanothrix, Sars. 
lll. Six pairs of thoracic limbs; the labrum provided with an 
appendage, Acantholeberis, Lilljeborg: appendage of labrum 
long, pointed, and setose. Intestine without caecum. 
Ilyocryptus, Sars: appendage of the labrum short, truncated. 
Intestine with a caecum. 
B. Both rami of second antenna three-jointed. 
Fam. 6. Lynceidae’: five or six equidistant pairs of thoracic feet. 
Intestine coiled. 
i. Six pairs of thoracic limbs. Head and thorax separated by a 
deep depression. Intestine with one caecum, stomach with 
two. Female carries many summer-eggs.  Hurycercus, 
Baird. 
il. Five pairs of thoracic limbs. Head and thorax separated by a 
slight groove or not at all. Anterior digestive caeca absent. 
Female carries only one or two summer-eggs. 
A. Body elongate, oval. 
a, Head carinate, the eye far from the anterior cephalic margin. 
Camptocercus, Baird: body laterally compressed. Second 
antennae with seven swimming hairs. Telson more than half 
as long as the shell. Acroperus, Baird (Fig. 23): body 
compressed. Second antennae with eight swimming hairs, of 
which one is very small. Telson less than half as long as 
the shell. 
b. Head not carinate, the eye near the anterior cephalic margin. 
Alonopsis, Sars: terminal claws of telson with three accessory 
teeth. Alona, Baird: terminal claws of telson with one 
accessory tooth (includes sub-genera Leydigia, Alona, Harpo- 
rhynchus, Graptoleberis). Peracantha, Baird (Fig. 14): terminal 
1 More properly Chydoridae, but the universally known name Lynceidae is con- 
venient. 
