GENUS HBLEOPEEA— HELEOPEEA PICTA. 163 



The shell of Heleopera pida is compressed ovoid, and never presents 

 the pyriform shape so common in Nebela. In the broad view of the shell, 

 it has an egg-like outline, the narrow end forming the convex line of the 

 mouth. In the narrower view of the shell, the outline is elliptical, and the 

 mouth appears as a deep angular notch. The mouth is transversely ellip- 

 tical, with angular commissures, as represented in fig. 1 1. 



The shell is composed of chitinoid membrane, and is transparent and 

 of a yellowish or pale raw sienna color. It presents a reticulated struc- 

 ture with polygonal meshes. Under higher powers, the Hues of the reticu- 

 lation appear to be composed of rows of granules, or they have a beaded 

 an-angement. The surface of the shell is not perfectly even, but is slightly 

 undulating, apparently from elevation of the reticulation above the level of 

 the intervening meshes. 



Occasionally irregular particles of hyaline quartz are incorporated 

 with the shell at the summit of the fundus, as seen in figs. 6, 7, 10. 



The sarcode of JSeleopera picta has a bright green endosarc from the 

 abundance of chlorophyl which enters into its composition. The chloro- 

 pliyl corpuscles usually measure from g^th to g^th of an inch in diameter; 

 but in different specimens and conditions of these, they range from gsso*^ *^ 

 g^th of an inch in diameter. 



A large clear nucleus occupies the centre of the sarcode, but is usually 

 more or less obscured from view by the surrounding chlorophyl corpuscles 

 and other, uncolored, elements. 



The sarcode occupies the greater part of the interior of the shell, 

 usually leaving but a small interval at the sides and fundus, as seen in 

 the view of the broad surfaces of the animal. It has the same means of 

 attachment to the fundus by threads of ectosarc as in Nebela and other 

 genera. 



Contractile vesicles, three or four at the same time, occupy the ordinary 

 position, at the periphery of the sarcode contiguous to the nucleus, as in 

 Hyalosphenia, etc. 



The pseudopods are large and numerous, and may be seen extending, 

 and often writhing snake-like, in all directions, from the capacious mouth. 

 They are commonly simple and cylindrical, with blunt ends, but they fre- 

 quently branch, and at times present pointed ends. They not unfrequently 

 extend the length of the shell, with a thickness of about ^th. of an inch. 



