

1891.] Rocky Mountain Rhizopods. , 1075 
All these species were to be found in very numerous individu- 
als; in fact, as numerous as 2,000 feet lower down. Yet to that 
dist ought to be added: Euglypha ciliata Leidy, one specimen , 
Trinema lineare Penard, one specimen; Assudina minor Penard, a 
very few specimens. 
An interesting fact seems to me to be that, with the exception 
of the very few individuals belonging to the three latter species, 
which I found after much exertion among hundreds and hundréds 
of other rhizopods, all the species mentioned in the list belong to 
the section of the Rhizopoda known as “ Lobosa,” —ż. e., with 
broad and blunt pseudopodia. The section “ Filosa,” * including 
those Rhizopods with filiform pseudopodia (Euglypha, Trinema, 
Sphenoderia, etc.), so rich in species, and yet more so in 
individuals, which generally swarm everywhere and outnumber 
the Lobosa, have been found to be practically absent at a height 
of 12,000 feet. My observations, which concern only a single 
locality, are not sufficient to enable me to draw from that absence 
any certain conclusions; yet, at any rate, they seem to show a 
remarkable difference in the vital resistance between those two 
great divisions of fresh-water Rhizopods. 
Among the species mentioned in the list I find two of them 
which must be dealt with at some length: 
Difflugia rubescens, sp. nov.—Very likely this form has been 
seen by Leidy; indeed, he figures two shells which I think | 
must be referred to this organism (Pl. x., Figs. 24, 25) as belong- 
ing to Difflugia pyriformis, and with the statement “ with brown 
endosarc.” But we have most certainly here a distinct species, 
which I shall call Diffugia rubescens. It was very abundant. I 
have examined several hundreds of specimens, which have all 
proved to be remarkably constant in form, size, and structure. 
The shell, pyriform, not compressed, not quite twice as long as 
broad (length, 0.030—0.035 mm.), consists first of a pellicle of 
clear chitinoid material, always covered with diatoms. These 
3 Leidy separates the fresh-water Rhizopods into two great divisions, Lobosa and 
Filosa. This corresponds, in fact, to two very natural groups; yet I must mention that 
a few Rhizopods (Cyphoderia, Cryptodifflugia, some Pseudodifflugia, and some Ameebe) 
show intermediate characters in their pseudopodia, which are capable of passing from 
one form to anotherin a comparatively very short time. 
