No. 2.] FRESH-WATER PROTOZOA. 49 



Colpidium Stein. 



Similar to Colpoda, but less compressed, and with an 

 undulating membrane in front. Mouth oblique, three- 

 cornered. A small peristome a third of the distance from 

 the front. Pharynx short; nucleus spherical, central. 

 Contractile vacuole posterior and dorsal. 

 C. striatum Stokes, Fig. 176 and Fig. 177. 

 C. sp. (?), Fig. 183. Referred with doubt to this genus. 



C. sp. (?), Fig. 194. A very large form, larger than any 

 described species of Colpidium. It may not belong to this 

 genus ; but at present I am unable to locate it elsewhere. 

 It is a moderately abundant animal. 



Glaucoma Ehrbg. 



Somewhat ovate, flattened. Mouth a quarter of the 

 distance from the anterior end, a little to the right; tri- 

 angular to crescent-shaped, with two undulating mem- 

 branes. Striation and ciliation regular. Nucleus spheri- 

 cal, central, and a secondary nucleus. 

 Gl. scintillans Ehrbg., Fig. 182. 

 Gl. scintillans (?) Ehrbg., Fig. 171. 



Fig. 207 represents a common minute infusorian that 

 appears to be Trichoda piira (Ehrbg.), which Biitschli 

 places with Glaucoma. I can detect no membranes in our 

 specimens, and prefer to retain the name Trichoda. 

 Dallasia Stokes. 



Elongated, rounded in front and contracting into a 

 tail behind. One side somewhat flattened, the other con- 

 vex. Mouth near the front and somewhat triangular, 

 with two membranes much like those of Glaucoma. 

 Contractile vacuole single ; nucleus single and central. 



D. frontonia Stokes, Fig. 175. In the specimens found here 

 the vacuole is posterior instead of anterior as described by 

 Stokes. 



Uronema Duj. 



Ovate, acute, anteriorly compressed, with the ventral 

 surface straight and the dorsal curved. Mouth in the 

 middle of the ventral surface or somewhat more forward, 

 surrounded by one or more undulating membranes. 

 From the mouth forward extends a furrow in which the 



