256 BULLETIN OF THE UNITED STATES FISH COMMISSION. 



ROTIFERA. 



Monostyla ovata, n. sp. 



Lorica broad ovate, truncate, antennae nearly as broad before as behind. Dorsal 

 outline regularly rounded, not recurved before. Lobe flat; ventral plate flat. Toe 

 with very distinct shoulder, however viewed. Front margins of both dorsal and 

 ventral plates entire. Dorsal plate strengthened by two diverging longitudinal ribs, 

 about equidistant from each other and from the lateral angles of the plate, rendering 

 the anterior margin slightly angulate where they join it and vanishing behind at 

 about the middle of the shell. Eye single, transverse, oval, red, situated just above 

 and before the mastax, with two very minute red points behind it. Foot and toe 

 about two- thirds as long as the lorica is wide. Ventral plate much shorter posteriorly 

 than dorsal, its posterior margin slightly excavated before the foot. 



Dimensions, 0.25 millimeter long by 0.18 millimeter wide. 



From warm spring (103 P.), Yellowstone Lake, August 3, 1890. 



Conochilus leptopus, n. sp. 



Resembling G. volcox. Antenna? adnate to the tip, where the pair are rounded 

 off as one; but very slightly bifid at the base of the two hairs. Stalk not swollen, 

 slender, tapering backward regularly from the slightly dilated point of attachment to 

 the body. Eyes black, about midway between cloaca! opening and edge of disk. 

 Cloaca about half of distance from the edge of the disk to the base of the expanded 

 body. Trophi slightly tiuted yellowish brown, not orange. 



Entire length, when expanded, 0.32 millimeter; extended stem, 0.13 millimeter; 

 breadth of body, 0.088 millimeter; expanded disk, 0.094 millimeter. 



Exceedingly abundant in spherical colonies in Yellowstone Lake, July and August, 

 1890, and also in Lewis Lake, Yellowstone Park, July, 1890. 



PROTOZOA. 



Stentor igneus, var. fuliginosus. 



Form turbinate, with slightly swollen sides, very slightly changeable, peristome 

 with spiral lobe, greatest width slightly more than half greatest length. Color soot- 

 black, given by blackish granules; when decolorized showing green as if by chloro- 

 phyl. 



Individuals when highly magnified gray by reflected or transmitted light, through 

 mingling of green and black. 



Form not symmetrical, the right side (when spiral lobe of peristome is uppermost) 

 being swollen below. When the peristomal lobe is at the side it appears as a tubercle 

 or projection. Form sometimes considerably shortened, so as not to be longer than 

 broad. Peristome angularly produced, so as to form with tip of spiral lobe an equi 

 ateral triangle, giving the entire animal an angular or trigonal shape. Tip flexible 

 and contractile, transparent when extended. 



Swarmed in Lake of the Woods August 20, 1890, forming soot-like collections as 

 a film on the surface among pond lilies (Nelumbium) and a discontinuous coating on 

 under sides of the same. 



