GENUS IIELEOPERA— HELEOrERA PETRICOLA. 165 



In the encysted condition of H. picta, the compressed globular ball is 

 more or less proportionate in size with that of the capacity of the shell ; in 

 different individuals it ordinarily ranges from ifh to ,-^th of an inch in 

 breadth. 



The mouth of the shell in the encysted condition of the animal is not 

 only closed by an epiphragm, but is more or less narrowed by the approx- 

 imation of the lips, and sometimes these appear closed)- glued together. 



HELEOPERA PETRICOLA. 



Plate XXVI, figs. 12-20. 



Shell compressed oval ; mouth terminal, broad, elliptical, convex down- 

 ward, with acute commissures ; fundus convex, loaded with quartz-sand. 

 Structure of shell of chitinoid membrane, reticular, with polygonal or 

 rounded meshes, transparent and colorless, but sometimes brownish. Sar- 

 code colorless ; pseudopods numerous. 



Size. — Length from 0.096 mm. to 0.15 mm.; greater breadth 0.068 mm. 

 to 0.09 mm. ; less breadth 0.048 mm. to 0.06 mm. ; breadth of mouth 0.052 

 mm. to 0.06 mm. by 0.015 mm. 



Locality. — Sphagnous swamps of Pennsylvania and New Jersey. Ab- 

 secom, Hainmonton, and Longacoming, New Jersey; Broad Mountain, 

 Schuylkill County, Pennsylvania. 



Heleopera petricola, represented in figs. 12-20, pi. XXVI, is found 

 in sphagnum in association with the former species, but is comparatively 

 rare. A few individuals I have met with every year since 1874, in 

 large swamps of New Jersey and Pennsylvania. In most cases I have 

 observed the animal in the quiescent or encysted condition, and rarely have 

 I seen it in an active state. 



The shell is compressed oval, with a very wide terminal mouth, the 

 line of which, in the broad view of the shell, is convex downward. The 

 fundus is convex, and is invariably more or less loaded with large, hyaline, 

 angular quartz-sand. 



In structure the shell appears to be composed of chitinoid membrane, 

 with a reticular arrangement, sometimes well marked, at others rather 

 indistinct. It is usually colorless, but is sometimes of a pale ferruginous 

 brown, probably due to the infiltration of iron oxyd, which is not unfre- 

 quent in sphagnous swamps. 



