234 



AQUATIC MICROSCOPY FOR BEGINNERS. 



sent, as it is in all the known American species, ex- 

 cept the one shown in Fig. 164. Sf. muticus is not un- 

 common. 



Fig. i65.-^Pterodina 

 patina. 



[2. PterodIna (Fig. 165). 



The lorica is almost circular, much flattened, and 

 perfectly transparent. The an- 

 terior border has a broad notch 

 with rounded margins, 6ver which 

 extends a lip with a central round- 

 ed projection. The ciliary disks 

 are two, and rather widely separ- 

 ated. There are usually two eye- 

 spots. The foot is long, tail- 

 like, 'exceedingly flexible, and 

 so wrinkled transversely that it 

 appears to be formed 

 of narrow rings. It 

 can be withdrawn en- 

 tirely into the lorica, and the Rotifer 

 seems to take pleasure in doing so. It 

 has no tail, but is terminated by a small 

 sucker bordered by a ring of fine cilia.- 

 The Rotifer is often seen among the leaf-' 

 lets of Ceratophyllum and other aquatic 

 plants. ' 



13. SCARIDIUM (Fig. 166). 



The transparent, glassy lorica is . rather 

 squarely vase-shaped, somewhat flattened, pj^ ,56_scar- 

 and generally has a tooth-like projection ' ■'*''""■ 

 on each side of the posterior border. The Rotifer 

 can always be recogflized by its two exceedingly long 



