206 FRESH- WATER RHIZOPODS OP NORTH AMERICA. 



The mouth is circular, and surrounded with a delicate, structureless, 

 membranous zone, as represented in figs. 20, 21. 



The shell of Campascus is dull yellowish or straw-colored, and is com- 

 posed of homogeneous chitinoid membrane incorporated with scattei'ed 

 sand particles. Even with high microscopic power I could detect no trace 

 of hexagonal structure, such as exists in the shell of Cyphoderia and Arcella. 



The soft part of the animal is like that of Cyphoderia or Euglypha. A 

 large, clear nucleus occupies the fundus of the sarcode mass, and in con- 

 tiguity with it, especially accumulated just beneath, there is a quantity of 

 oil-like molecules. The adherent sand particles to the shell prevented me 

 from detecting contractile vesicles, which no doubt exist in a corresponding 

 position to that in Cyphoderia or Euglypha. The pseudopods are like 

 those of the latter animals The shell of Campascus is commonly about 

 0.125 mm. in length. 



EUGLYPHA. 



Greek, eu, well; gluplie, sculptured. 

 Eughjplia: Dujardin, 1841. Difflugia : Ehrenberg, 1841. Assulina; Setigerclla : Ehrenberg, 1871. 



Animal provided with a hyaline, ovoid shell, of uniform diameter, 

 or compressed, composed of regular, oval or hexagonal plates of chitinoid 

 membrane, arranged in alternating longitudinal series. Mouth terminal, 

 circular or elliptical, with the marginal plates forming a series of minutely 

 serrulate angular points. Shell mostly provided with spines or hairs, though 

 sometimes absent. Sarcode colorless, with a large nucleus in the fundus, 

 and usually several contractile vesicles occupying an intermediate position 

 of the mass. Pseudopods filamentous, exceedingly delicate, dichotomously 

 branching, not anastomosing, and with no evident circulation of granules. 

 Animal when in motion with the shell erect or jDerpendicular, with the 

 mouth downward, and with the pseudopods more or less horizontally 

 divergent. 



The genus Euglypha contains a number of distinct or well-marked 

 forms which are conveniently considered to be so many species; but, through 

 a multitude of intermediate conditions, the species appear to graduate into 

 one another. They are the most elegant and complex in the structure of 

 their shell of any of the Protoplasts provided with such a covering. 



The shell of Euglypha is composed of plates, mostly of uniform size, 



