stokes.] ■^"14 [Sept. 16, 



Notices of NeiD Fresh-water Infusoria. By Alfred (J. Stokes, M.D., Trenton, 



N.J. 



{Read before the American Philoso2)hical Society, September 16th, 1SS7.) 



Hexamita spiralis, sp. nov. Fig. 1. 



Body elongate obovate, about four times as long as broad, the anterior 

 extremity rounded, the posterior obtusely pointed ; anterior flagella four 

 in number, vibratile, arising close together, their length diverse but ex- 

 ceeding that of the body, the two shortest extended opposite each other at 

 right angles to the body, their distal extremities curved forward ; the 

 remaining two extending backward, each forming a long, loose spiral ; 

 trailing flagella two, arising from the tip of the posterior extremity, and 

 exceeding the body in length ; contractile vesicles two, situated opposite 

 each other in the anterior body -half ; nucleus obscure. Length of body, 

 ^250 inch. Hab. — The intestinal canal of the tadpole of the common 

 toad. Movements by rapid rotation on the longitudinal axis. 



This differs from previously observed species in the presence of two con- 

 tractile vesicles, and in the spiral disposition of two of the anterior 

 flagella. 



Petalomonas dorsaUs, sp. nov. Fig. 2 ; diagram. 



Body broadly ovate or suborbicular, colorless, transparent, the length 

 but slightly exceeding the breadth ; the anterior extremity the narrower, 

 evenly or obliquely rounded, occasionally obliquely truncate ; posterior 

 border rounded, sometimes eraarginate ; dorsal surface longitudinally 

 traversed by a central, strongly compressed keel-like and upright plane, 

 or broad wing, the superior margin of which is evenly convex ; ventral 

 surface somewhat concave, a transverse optic section of the body present- 

 ing a triradiate appearance, the re-entering, dorso -lateral and ventral 

 angles rounded ; oral fossa conspicuous, from which apparently issues a 

 flagellum subequal to the body in length ; nucleus subcircular hi outline, 

 placed near the centre of the left-hand body margin ; contractile vesicle 

 single, small, located on the left-hand side of the dorsal ala near the body 

 centre ; endoplasm coarsely granular. Length of body, -gl^ to g^^ inch. 

 Hab. — Standing pond water. 



This is readily recognizable from P. carinata, for -which it might per- 

 haps be mistaken, by its much larger size, and by the very conspicuously 

 developed centro-dorsal, upright plane. In P. carinata the dorsal eleva- 

 tion is low and ridge-like, and although the lateral surfaces of this part 

 are usually evenly sloping or slightly convex, they are at times notice- 

 ably concave. In P. dorsalis the dorsal ala is usually as high as one-half 

 the width of the body. The part seems especially liable to deformity, 

 often being observed to be variously indented, or distorted and developed, 

 to one side or the other of its normal central position. 



