New American Fresh-water Infusoria. By Dr. A. C. StoJces. 39 



transversely ; pedicle short, slender ; contracted body obovate, the sub- 

 spherical central region then thrown into several annulations over the 

 posteriorly tapering portion. Length of body 1/300 to 1/346 in. 

 Habitat, shallow pools with algae in early spring. Solitary or few 

 together. 



Pyxidium invaginatum sp. no v., fig. 15. 



Body elongate urceolate, often somewhat gibbous, rather more than 

 twice as long as broad, widest centrally, constricted anteriorly to form a 

 short, neck-like region, and tapering posteriorly to produce a subcylindrical 

 prolongation forming about one-third of the entire length of the zooid, 

 a transverse cuticular fold usually encircling the body at the origin of 

 the posterior prolongation ; pedicle very short, usually only about one- 

 fourteenth as long as the entire body ; the cuticular surface finely striate 

 transversely ; ciliary disc conspicuous, furnished with two circles of cilia ; 

 peristome border truncate, crenulate, not everted, apparently supporting 

 a conspicuous, collar-like membrane ; contracted zooid ovate, frequently 

 nodding, the posterior prolongation always invaginate within the central 

 body-region, and the short pedicle invaginate within the posterior pro- 

 longation; vestibulum capacious, extending beyond the centre of the 

 body, its walls cilia te at intervals; endoplasm colourless, transparent; 

 contractile vesicle single, spherical, near the body-centre, and apparently 

 communicating with the vestibulum. Length of the zooid, including 

 pedicle, 1/300 in. Habitat, pond water; attached to the rootlets of 

 Lemna. 



This very characteristic Pyxidium is readily recognizable and easily 

 separable from all previously recorded members of the genus, by the 

 presence of the double posterior invagination so conspicuous in the con- 

 tracted zooid. The cuticular striations are so extremely fine that they 

 can be observed with difiiculty, except when under the influence of 

 oblique light. 



Vaginicola annulata sp. no v., fig. 16. 



Lorica broadly vasiform, somewhat more than twice as long as wide, 

 rounded and inflated posteriorly, the frontal region slightly narrowed, 

 the anterior border everted and narrowly re volute, the posterior region 

 encircled by a single annular and horizontal inflation; the inclosed 

 animalcule elongate obconical, the length about four times the width of 

 the peristome, projecting, when extended, for about one-third its length 

 beyond the lorica ; peristome abruptly widened, twice as broad as the 

 body, the ciliary disc obliquely elevated ; cuticular surface transversely 

 striated ; contractile vesicle single, spherical, situated near the anterior 

 border, apparently within the ciliary disc. Length of lorica 1/204 in. ; 

 length of extended zooid 1/150 in. Habitat, pond water. 



The posterior annulation encircling the lorica and the very anterior 

 position of the pulsating vacuole distinguish this species from the other 

 members of the genus. The zooids are frequently to be seen inhabiting 

 the same protective sheath. The latter changes to a transparent brown 

 colour with age. 



