Infusoria from American Fresh Waters. Ill 



The most posterior of the five ventral styles is so intimately 

 connected with the anterior group of anal uncini that careful 

 scrutiny is usually needed to positively observe it. Its func- 

 tions, however, its habit of curving forward, and its flexi- 

 bility readily distinguish it from the anal cluster. The 

 elements of the latter are rigid and unbending, only the one 

 on the extreme right usually having great freedom of move- 

 ment. The extremities of the two forming the posterior 

 group are often fimbriated. 



With this, as with Oxytricha liymenostoma^ there is some 

 appearance of a double peristomial membrane ; but it is not 

 conspicuous nor even very distinct. 



Oxytricha hymenostoma^ sp. nov. (PL III. fig. 10.) 



Body subelliptical, soft and flexible, about twice and a 

 half as long as broad, both extremities rounded, the left- 

 hand region of the frontal border somewhat oblique, the left- 

 hand body-margin slightly concave anteriorly; lip short, 

 crescentic ; frontal styles five uncinate and three setose ; ven- 

 tral styles five — two near the apex of the peristome-field, one 

 central, two near the anal styles ; the latter five in number, 

 the three on the right-hand side usually projecting beyond 

 the body ; marginal setge continuous, larger and longer on 

 the posterior border ; peristome extending to the centre of the 

 ventral surface, the right-hand margin ciliated and bearing 

 apparently two membranes of unequal widths the left-hand 

 border furnished with a series of very fine paroral cilia ; nuclei 

 two, ovate ; contractile vesicle spherical, near the centre of 

 the left-hand border. Length of body -g^xj to 2 su inch. 



Hob. Hay-infusion. Movements rapid. 



The appearance of two peristomial membranes is very 

 distinct, and has been observed in all the numerous individuals 

 examined. Their presence is unique, so far as the Oxytrichce 

 are concerned, and my impression is that such an addition 

 to the not uncommon single membrane has not been previ- 

 ously recorded with any other member of the Hypotricha. 



Oxytricha acuminata^ sp. nov. (PI. III. fig. 11.) 



Body elongate-lanceolate, soft, flexible, and posteriorly 

 somewhat extensile, about six times as long as broad when 

 extended, the frontal border rounded and projecting as a soft, 

 flexible, prominent lower lip; posterior extremity pointed, 

 tapering ; frontal styles eight or ten ; ventral uncini five — 

 three anteriorly placed, two near the five anal styles, the 



