222 FRESH-WATER RHIZOPODS OF NORTH AMERICA. 



composed of oval, imbricating plates, in longitudinal alternating series, the 

 overlapping borders producing hexahedral areas limited by zones of minute 

 ellipses; oral row of plates like the others, and not forming angular teeth to 

 the mouth as in Euglypha. The lateral acute border of the shell fringed with 

 movable subulate spines articulated with the shell by a minute knob, usually 

 in pairs, sometimes single and rarely triple. Soft structure as in Euglypha. 



Size. — Ranging from 0.1 mm. to 0.136 mm. long and 0.08 mm. to 0.096 

 mm. in the greater and 0.036 mm. to 0.06 mm. in the less breadth ; mouth 

 0.04 mm. to 0.06 mm. wide ; spines 0.016 mm. to 0.04 mm. long. 



Locality. — In the moist sphagnum of the cedar swamps of Absecom, 

 Atco, and Malaga, New Jersey. 



Placocista spinosa I suppose to be the same as the Euglypha spinosa 

 discovered and described by Mr. Carter from specimens found in heath- 

 bogvvater, in South Devon, England. Mr. Carter states that he saw only 

 two or three specimens, and those in the winter, when the animal was in a 

 passive condition.* Since then the creature appears to have been observed 

 only by Mr. Archer of Dublin. Schulze, who had not seen it, considers 

 it to be only a variety, or resting condition, of Euglypha compressa,f which 

 I view as the same as E. ciliata, described in the preceding pages. 



PBacocista spinosa usually exceeds in size any of the species of 

 Euglypha, though I have occasionally found specimens of E. alveolata that 

 were larger. It is completely colorless and hyaline, and is only rendered 

 more or less opaque white about the middle zone of the body from the 

 accumulation there, in the sarcode, of variable proportions of fine oil-like 

 molecules By reflected light it exhibits a silvery white lustre. 



The shell is compressed oval, sometimes with the oral pole feebly 

 tapering, and in the broader view with the fundus broadly convex. The 

 lateral borders meeting at the fundus are acute. The mouth is a wide, 

 transverse, elliptical aperture, with acute commissures and an entire margin. 

 Its broader line is more or less convex downward, but often also projects 

 more downward at the commissures. See pi. XXXVIII. 



The shell is composed of oval plates arranged in alternating longitudi- 

 nal series, overlapping at the borders so as to produce hexahedral areolae 



* Annals and Magazine of Natural History, 1865, xv, 2.90. 

 t Archiv f. inikros. Anatomic, 1875, xi, 104. 



