ENTOMOSTRACA AND PHYLLOPODA. 251 



lengthwise. The beak is blunt, and usually curved 



downward, or it may extend slightly away from the 



body. The head is strongly arched. 



The teeth on the posterior border (not 



shown in the figure) are small, and 



vary from one to four. The eye is 



small. The eggs are carried in a 



brood cavity. The animal occurs chiefly in lakes and 



large ponds. 



7. CHYDORUS (Fig. 163). 

 The surface of this nearly spherical shell is usually 



reticulated. The beak is long, curved, and pointed, 



being sharp in the female. The posterior border is 

 truncate in young specimens, becoming 

 more rounded in the old. The eye is 

 present and single. The eggs are hatched 

 in the brood cavity. The animal occurs 



Fig. 163.-Chydoms. abundantly yerj ear]y in the gprmg) usu . 



ally near the bottom, living chiefly on vegetable mat-, 

 ters. The motion is rolling and somewhat unsteady, 

 and uncertain in appearance. 



8. ALONOPSIS (Fig. 164). 



The lower or free edge of the shell is fringed with 

 bristles, which are longest in front. 

 The beak is long, pointed, and separat- 

 ed by some distance from the body of 

 the shell. Eye large. One of the feet 

 (the third) has a long spine fringed with "pig. icL-Aionopsis. 

 12 



