1887.] -^y [Stokes. 



the body-centre in width, the border thickened ; pedicle from five to six 

 times as long as the body ; nucleus apparently ovate, anteriorly placed ; 

 contracted body subspherical, invaginating the extremity of the pedicle. 

 Length of extended body, j^'y^j inch. Hah. — Pond water; attached to 

 rootlets of Lemna. Solitary. 



Voriicella mollis, sp. nov. 



Body conical carapanulaie, somewhat changeable in shape, widest ante- 

 riorly, tapering posteriorly, the length scarcely exceeding the width ; 

 peristome broad, flattened, crateriform, equaling in width the body- 

 length, the border not revolute ; cuticular surface verj' minutely tubercu- 

 late ; contractile vesicle double ; pedicle from sixteen to eighteen times as 

 long as the body ; contracted body subspherical. Length of the extended 

 zooid, -j-J^ inch. Hub. — Pond water ; attached to rootlets of Lemna. 

 Solitary. 



Voriicella aqua-dtilcis, sp. -nov. Fig. 12. 



Body ovate or pyriform, very slightly changeable in shape, less than 

 twice as long as broad, slightly constricted beneath the peristome border, 

 the cuticular surface strongly and conspicuously striate transversely ; 

 peristome more than one-half the body-centre in breadth, but not equal- 

 ing it, the border thickened, not everted ; ciliary disc obliquely elevated ; 

 pedicle from two to three times as long as the body. Length of body, yi^ 

 inch. Hub. — Fresh water ; attached to rootlets of Lemna. Solitary, or 

 few together. Contracted body obovate. 



Vorticella platysoma, sp. nov. Fig. 13. 



Body ovate or pyriform, less than twice as long as broad, the anterior 

 body region subspherical, the posterior tapering to the pedicle ; cuticular 

 surface transversely striate ; peristome equaling the body-centre in width, 

 the border revolute ; the ciliary disc not elevated ; nucleus band-like, 

 curved, transversely placed in the anterior body-half; pedicle seldom ex- 

 ceeding the body in length. Length of body, xiV? inch. Hab. — Pond 

 water ; attached to Alga;. 



Oi')ercularia allensi, sp. nov. Fig. 14. 



Bodies elongate-fusiform or subvasiform, more than three times as long 

 as broad, widest centrally, tapering posteriorly to the pedicle, constricted 

 beneath the peristome, the cuticular surface very finely striate trans- 

 versely ; peristome border everted, minutely crenulate ; ciliary disc very 

 obliquely exerted ; ciliary circles two ; membranous collar large and 

 conspicuous ; nucleus band like, short, curved, transversely placed in the 

 anterior body-half ; contracted zooid suddenly pendent, obovate, usually 



PROC. AMER. PHILOS. SOC. XXIV. 126. 2F. PRINTED OCT. 22, 1887. 



