Infusoria from American Fresh Waters, 113 



Histrio inquietuSj sp. nov, (PI. III. fig. 13.) 



Body elongate-obovate, about three times as long as broad, 

 the extremities rounded ; marginal setee uninterrupted ; anal 

 styles five, occasionally six. the extremities often finely fim- 

 briated ; peristome-field obovate, capacious, slightly curved 

 towards the left-hand side, the right-hand margin ciliate and 

 bearing an undulating membrane continued around the ante- 

 rior border ; nuclei two, ovate ; dorsal hispid setse present. 

 Length of body -jIf inch. 



Hah. Standing pond-water, with Lemna. Movements 

 rapid. 



Histrio complanatus^ sp. nov. (PI. III. fig. 14.) 



Body subelliptical, much depressed, twice as long as broad, 

 the posterior extremity obscurely pointed, the anterior evenly 

 rounded ; frontal lip crescentic, conspicuous ; peristome-field 

 extending to near the centre of the ventral surface, the right- 

 hand margin ciliated and bearing a membrane 5 frontal styles 

 eight, five uncinate, with three smaller and setose ; ventral 

 styles five, one central, with two anteriorly and two poste- 

 riorly placed ; anal styles five, the three on the right-hand 

 side alone projecting beyond the body-margin ; marginal setge 

 uninterrupted, longest and largest posteriorly; nuclei two, 

 ovate ; contractile vesicle spherical, situated near the centre 

 of the left-hand border of the dorsal surface. Length of body 

 -3-^^ inch. Dorsal hispid setse short and inconspicuous. 



Hah. Shallow pools in early spring. 



The position of the contractile vesicle beneath the cuticular 

 surface of the dorsum is well marked, and the enclosed fluid 

 is evidently expelled through that surface. 



As in most of the Hypotricha possessing what has been 

 called the upper lip, this part is really not a continuation of 

 the dorsum, but more nearly of the ventral surface, and the 

 adoral cilia lie above the projection until they leave the ante- 

 rior border to pass to the left-hand margin of the peristome- 

 field. This structural arrangement holds true in a majority of 

 the lip-bearing Hypotricha, I believe in all. 



Euplotes variabilis^ sp. nov. (PI. III. fig. 15.) 



Body elongate-obovate, nearly twice as long as broad, 

 frontal border truncate ; the lip prominent, crescentic ; right- 

 hand side of the posterior extremity obliquely truncate or 

 somewhat concave, the left-hand side of that border rounded : 



Ann. & Mag. N. Hist. Ser. 5. Vol. xx. 8 



