278 FRESH-WATER RHIZOrODS OF NORTH AMERICA. 



Locality. — Among moist moss, in association with Rotifer vulgaris, 

 Trinema acinus, Bifjlugia constricta, tardigrades, anguillulas, diatoms, and 

 desmids, in the crevices of pavements, in shaded places, in the city of 

 Philadelphia. 



The genus Gromia was discovered and described by the French 

 naturalist Dujardin, in 1835, from a species occurring among corallines 

 and other marine algae on the coast of France. A few years later the same 

 acute observer described a second species, Gromia fluviat'dis, discovered on 

 hornwort, Ceratophylhim, in the river Seine. 



The genus is of special interest, because it is a representative, in the 

 simplest condition, of that great order of Rhizopods, the Foraminifera, 

 which are exclusively marine, with the exception of the present one. 



The animal I have named Gromia terricola I discovered in the 

 summer of 1874, among moss growing in the crevices of the pavement, in 

 the yard attached to my home, in the city of Philadelphia. It was asso- 

 ciated with abundance of the common Wheel-animalcule, Trinema encliehjs, 

 Dijflugia cassis, Euglyplia atveolata, anguillulas, tardigrades, diatoms, des- 

 mids, etc. 



On several occasions, having observed half a dozen individuals, I 

 was led to believe it was common, but I have since failed to find it after 

 frequent search in the same and similar localities. Nor have I been so 

 fortunate to find any other Gromia, a circumstance I have greatly 

 regretted, from the feeling that, with the experience gained in the investi- 

 gation of rhizopods, after several years I would have been better able to 

 resolve its characters. 



Gromia terricola, represented in figs. 1-3, pi. XLVII, has a spherical or 

 slightly oval, translucent body. By reflected light it is white or cream- 

 colored ; by transmitted light of a pale yellowish color. The investing 

 membrane or shell is thin, transparent, homogeneous, and colorless or feebly 

 yellowish. It is smooth, but usually has more or less adherent dirt con- 

 sisting of fine granules and coarser particles of quartz-sand. See figs. 1, 2. 



In the individuals observed, the mouth was obscure, and its exact 

 character I neglected to determine. 



The interior of the body was composed of a pale granular protoplasm, 

 with scattered oil molecules, completely filling the shell. It contained a 



