162 FRESH-WATER RHIZOPODS OF NORTH AMERICA. 



measured .-^th of an inch in the greater breadth, and two .^,th of an 

 inch; the less breadth was ith of an inch. The mouth was j^- th by j^th 

 of an inch. 



HELEOPEKA. 



Greek, helos, a bog; pera, a bag. 



Shell compressed ovoid, composed of cancellated, chitinoid membrane 

 presenting a reticulated appearance of mostly dotted or interrupted lines, 

 often at the fundus incorporated with particles of sand. Mouth inferior, 

 terminal, large, transversely elliptical. Sarcode and its constituents as 

 usual in Hyalosphenia and Nebela. Pseudopods numerous, digitiform. 



HELEOPERA PICTA. 



Plate XXVI, figs. 1-11. 



Difflugia (Xebela) splwgni. Leidy: Proc. Ac. Nat. Sc. 1874, 157. 

 Nebela sjphagni. Leidy: Proc. Ac. Nat. Sc. 187(5, 119, figs. 16,17. 



Shell compressed ovoid, with the oral pole narrower; mouth terminal, 

 forming a broad narrow ellipse with acute commissures, convex downward 

 in the length, and appearing as an acute notch from the narrow sides. 

 Shell composed of a yellowish, transparent chitinoid membrane with a 

 reticular structure; the meshes of the net being polygonal and the lines of 

 the net dotted. Sarcode with bright-green endosarc from the multitude of 

 chlorophyl corpuscles entering into its constitution. Pseudopods numerous, 

 long, digitate, simple, and branched. 



Sue —Length 0.092 mm. to 0.168 mm.; breadth 0.076 mm. to 0.136 

 mm.; thickness 0.044 mm. to 0.072 mm.; mouth 0.036 mm. by 0.016 mm. 

 to 0.072 mm. by 0.032 mm. 



Locality. — Frequent and abundant in the sphagnous swamps of Penn- 

 sylvania and New Jersey. 



Heleopera picta, represented in figs. 1—11, pi. XXVI, I formerly 

 included in the genus Nebela as Nebela sphagni, but now regard it as 

 sufficiently peculiar to consider it as the type of another genus. 



The animal is found abundantly in almost every extensive sphagnous 

 swamp in association with various species of Hyalosphenia, Nebela, and 

 other rhizopods. It has the same bright coloring as Hyalosphenia pap'lio, 

 but has appeared to me of less graceful proportions and beauty. 



