GENUS PLACOCISTA— PLACOCISTA SPINOSA. 221 



the neck at variable distances from the mouth. See figs. 5-10, pi. XXXVII. 

 The spines are of variable length, usually long, curved and jDointed. 

 Rarely, I have seen them straight, with thickened ends and oar-like, as seen 

 in fig. 7. Rarely, also, I have seen a specimen with two rows of spines, 

 as in fig. 6. 



Occasionally also, in this species, the spines are absent; at least, in one 

 instance I observed a pair of individuals in conjugation, in one of which 

 the shell had a pair of spines, and in the other there were none. 



Euglypha brachiata is found in the same kind of localities as E. cristata 

 and E. mucronata, but is comparatively rare. I once found it in considera- 

 ble numbers in ooze from the headwaters of Batsto River, New Jersey. 



Euglypha tegulifera, a Fresh-water Rhizopod, recently described under 

 this name by Professor Barnard, in the American Quarterly Microscopical 

 Journal, 1879, 85, pi. viii, fig. 4, I have not seen. It was found among 

 algae in New York. Its characters would refer it to a different genus from 

 Euglypha. 



PLACOCISTA. 



Greek, plax, a plate; kiste, a box. 

 Euglypha: Carter. 



Animal with a compressed oval, hyaline, colorless shell, with acute 

 border and terminal elliptical mouth; the border of the latter entire, with 

 acute commissures. Shell composed of longitudinal rows of alternating 

 oval or roundish plates overlapping at their contiguous borders, so as to 

 produce hexahedral areas limited by zones of minute ellipses. Lateral 

 borders and fundus furnished with acuminate spines articulated with the 

 shell. Sarcode and pseudopods as in Euglypha. 



The genus is founded on what I take to be the Euglypha spinosa of 

 Carter, the shell of which differs from that of the characteristic species 

 of Euglypha, in having the mouth entire or destitute of dentate scales, and 

 in the possession of articulated spines. 



PLACOCISTA SPINOSA. 



Plate XXXVIII. 



Euglypha spinosa. Carter: An. Mag. Nat. Hist. 18G5, xv, 290, pi. xii, fig. 13. — Archer: Quart. Jour. 

 Mic. Sc. 1872, xii, 90; 1876, xvi, 237.— Leidy: Pr. Ac. Nat. Sc. 1874, 226; 1878, 172. 



Shell transparent, colorless, compressed oval, with acute lateral borders, 

 sometimes slightly tapering toward the oral pole ; mouth large, transversely 

 elliptical, with acute commissures and entire or edentulous border. Shell 



