336 CRUSTACEA 



Family 3. BOSMINIDAE. 

 First antennae greatly elongated and extending from the beak forms 

 a long curved proboscis; 5 pairs of feet and rudiments of the sixth; 

 second antennae small; pigment spot (accessory eye) wanting; intestine 

 straight and without liver sacs: 1 genus. 



BoSMlNA Baird. With the characters mentioned above: about 20 

 species; mostly bottom forms. 



B. longirostris (0. F. Mliller) (Fig. 521). 

 Shell o\al with hexagonal markings and with 

 \ a caudal spine projecting from the ventral 

 margin; length .35 mm.: very common in east- 

 em and central America; Europe. 

 Pjg 521 Family 4. LYNCEIDAE. 



^'""""fHeSr"*'''" Second antennae small, each branch of 



^' a^ntenna^r^i,' egg^Tn ^ each consisting of 3 segments ; pigment spot 

 the brood sac. (accessory eye) very large; intestine bent or 



coiled and usually without liver sacs: the largest cladoceran family, 

 containing about 20 genera. 



Key to the genera of Lynceidae here described : 



«! Intestine not coiled or bent 1. Eurycercus 



Cj Intestine coiled. 



6i A dorsal keel on head 2. Acroperus 



hz No keel. 

 Ci Body oval or elongate. 

 d^ Outer margin of post-abdomen concave in outline ; second antennae 



with 7 long setae 3. Graptoleberis 



(Zo Outer margin of post-abdomen straight, 



Ci Terminal claw of abdomen with 1 basal spine 4. AloiMA 



C2 Two basal spines present 5. Pleuroxus 



Co Body globular ; animals minute (3. Chydorus 



1. Eurycercus Baird. Body large and oval with short antennae; 

 intestine bent like an S and witli liver sacs: 1 species. 



E. lamellatus (0. F. Miiller) (Fig. 522). Body very large, being 

 sometimes 3 mm. long ; hinder side of the abdomen serrate : central 

 states; Europe. 



2. Acroperus Baird. Body minute, elon- 

 gate, with a long, broad abdomen; head and 

 back with a keel; shell with diagonal mark- 

 ings; intestine coiled: 3 species. 



A. harpae Baird (Fig. 523). Body truncate 



behind ; length .7 mm. : widely distributed over Fig. 522 — Eurycercus lamel- 



' .V, ?a<«s (Sussw. F. Deut.). 



eastern and central America ; Europe ; common. 



3. Graptoleberis Sars. Body minute, elongate; posterior margin 

 straight; second antennae with 7 long setae: 1 species. 



