156. MR. G. H, WAILES ON FRESHWATER 



Genus AWERINZEWIA. 



AwERiNZEWiA CYCLOSTOMA i^PenarcT), ScJiouteden. 

 Syu. Heleopera cydostoma, Peuard. 



Not common. It is very similar in size and appearance to Heleopera 

 petricola var. ametht/dea, Pen., but the aperture, instead of being linear and 

 wide, is small and oval, and is surrounded by a more or less thickened internal 

 border, the thickening taking place gradually on the inside of the test. 



The test is noticeable for the opaque whitish plates scattered on a bright 

 amethystine groundwork. The usual size is about 150 /i in length; those 

 found here were rather small, measuring about 130 /u, in length. 



Genus Centropyxis. 



Centropyxis ACULEATA, Stein. 



Of this usually numerous species only one individual was observed. 



C. ARCELLOIDES, Fencird. 



Several seen, about 70 /a in diameter. 



C. LAEVIGATA, Feuard. 



Not common. Diameter 80-120 /ju. 



Genus Difflugia. 



DUTLUGIA ARCULA^ Leidij. 



Syn. Triyonopyxis arcula (Leidy), I'enard, q. v. 



D. GONSTRICTA, Le'uhj. 



Numerous. Length 50-90//.. 



D. OBLONGA, Ehrenb. 



Syn. D. pyriformis, Perty. 

 Rare. Length 80-100 ^L. 



D. PRISTIS, Penard. 

 Rare. Length 65 /i. 



Genus Heleopera. 



Heleopera sordida, Penard. (Rev. Suisse Zool. 1910.) 

 Below the average size, often with but few adherent particles on the crown 

 of the test. Length 45-55 yu,. 



