lirachwnaea.] THE INFUSORIA. 419 



in summer, among lemna and Ceratophyllum. Length 

 about l-120th. 



73 1 . Pterodina elliptica. The elliptical Pterodina has 

 a membranaceous elliptical lorica, with a narrow, smooth 

 margin, the front entire (not excised). The two wheels 

 are united by a brow furnished with setae. The eyes 

 are distant. Found amongst conferva. Length l-120th 

 to 1 -108th. 



732. Pterodina clypeata {Brachionus clypeatns, M.) 

 The shield-like Pterodina has a membranaceous oblong 

 lorica, narrow, and smooth at the margin; it has a frontal 

 portion, or brow, connecting the two wheels, but destitute 

 of setae. The eyes are approximate. Fig. 505 is a dorsal 

 view, with the wheels extended. Found in sea water. 

 Length 1-1 20th; the shell, 1- 144th. * 



2e2 



