216 FRESH-WATER RHIZOPODS OF NORTH AMERICA. 



of the sides. They sometimes form a single row in the median line of the 

 lateral border, and at others a double row of variable regularity on each 

 side of the lateral border. They are mostly single or isolated, but not 

 unfrequently occur in pairs arising from the same point. 



The form with the lateral fringe of spines or hairs, as represented in 

 figs. 1-14, constitutes the species described by Carter and Schulze under the 

 name of Euglypha compressa, and appears to be the same as that previously 

 described hj Ehrenberg as Difflugia ciliata. 



With the more characteristic form, as indicated in the above descrip- 

 tion, in our sphagnous swamps, there occurs another in association with it, 

 in which the shell is more or less invested with delicate spines or hairs, 

 except in a zone of variable extent contiguous to the mouth. This hairy 

 form has been indicated by Ehrenberg under the name of Difflugia strigosa. 

 Specimens are represented in figs. 19, 20, pi. XXXV, figs. 16-20, pi. 

 XXXVI, and figs. 30, 31, pi. XXXVII, and may be regarded as a variety 

 with the name of Euglypha strigosa. 



The spines or hairs of Euglypha ciliata vary not only in number, but 

 also in length and strength, and sometimes they are altogether absent, as in 

 the specimen of fig. 23, pi. XXXVI. Sometimes they are very short, as 

 seen in fig. 8; sometimes of considerable length, as seen in fig. 19. In well- 

 developed characteristic individuals, the spines are stout and subulate, and 

 diverge outwardly with an inclination upward, as seen in figs. 1-5. When 

 more numerous, and especially in the variety E. strigosa, they are more 

 delicate, hair-like, or rather like rigid cils, as seen in figs. 7, 14, 16-20. 



The shell of Euglypha ciliata ordinarily appears to be composed of 

 somewhat elongated hexahedral plates of mostly uniform size, and closely 

 fitting together in longitudinal rows and alternating series. The plates pre- 

 sent a single intervening line; though in a different focus, they may be made 

 to appear with a double outline, as represented in fig. 23. Though such 

 seems to be the construction of the shell ordinarily, yet in a number of 

 instances I have met with individuals, which I viewed as of the same species, 

 having the shell composed of overlapping oval plates, as in Euglypha alveo- 

 lata, and as represented in figs. 3, 4. I think the difference did not depend 

 on an optical illusion, for in many empty cells of E. ciliata the octagonal 

 plates were as distinctl}- marked as a pen-and-ink sketch, and by no altera- 

 tion of the focus could I induce the appearance of overlapping plates with 

 hexahedral areas enclosed in zones of minute elliptical areas. 



