116 FEESH-WATEE EHIZOPODS OF NOETH AMEEICA. 



A large specimen, referable to D. lobostoma, from Jacksonville, Florida, 

 is represented in fig. 8, pi. XVII. It had a six-lobed mouth, with deep 

 sinuses, separated by angular points. In all respects it closely resembled 

 one, of which the mouth is represented in fig. 12 of the same plate, of 2>. 

 corona, from Lake Hattacawanna, New Jersey, except that it was devoid 

 of spines to the summit. At the side of the latter it might be regarded as a 

 spineless variety of the same species. 



Another specimen, from Hammonton pond, Atlantic County, New Jei'- 

 sey, represented in figs. 18, 19, pi. XV, may be regarded as a transitional 

 form from D. lobostoma to B. corona or D. urceolata. The shell is larger 

 than usual in D. lobostoma, is nearly spherical, provided with a short neck 

 and a feebly crenulated mouth, in which the crenulations are seen to be 

 about eleven. It is composed of thin angular plates, apparently consisting 

 of diatoms and fragments of others. 



As before intimated, Difflugia lobostoma is the commonest of our species, 

 and is found in the superficial mud and flocculent matter of most fresh-water 

 ponds and ditches. I have also frequently found it among the filamentous 

 algae and the materials adherent to aquatic plants. When first noticed after 

 removal to the field of the microscope, it is usually seen lying on the side. 

 Protruding its finger-like pseudopods, commonly about half a dozen, after 

 some apparent struggling it rises on end, generally with the mouth down- 

 ward. On tapping the slide upon which it is examined, it either firmly 

 maintains its position, or withdrawing the pseudopods it falls again on the 

 side, and usually much labor and patience are required to get the creature 

 in such a position as to see the mouth. From the common occurrence 

 of D. lobostoma, with the circumstance that, as ordinarily seen, it so much 

 resembles the B. proteiformis of Ehrenberg, I have been led to suppose 

 that it is the former, which is usually regarded as the latter by authors. 



I have repeatedly seen Difflugia lobostoma in conjugation, mostly two 

 individuals, but in several instances three together, so as to give a view in 

 outline comparable to the trefoil-shape of the mouth of the commonest 

 variety. 



DIFFLUGIA ARCULA. 



Plates XV, flgs. 34-37 ; XVI, figs. 30, 31. 



Shell hemispheroidal; fundus convex; base inverted, shallow infun- 

 dibuliform; mouth inferior, central, trilobed. Structure of shell usually 



