GENUS OXYTRICHA. 787 



periphery ; anal styles large, but not reaching to the posterior extremity of 

 the body. Length 1-144". Hab. — Fresh water, 



Oxytricha fallax, Stein. Pl. XLV. Fig. 7. 

 Body ovate, flattened, two and a half times as long as broad, rounded 

 and widest posteriorly, tapering towards and bluntly pointed at the 

 anterior end ; peristome-field wide, extending backwards nearly to the 

 centre of the body ; its reflected inner border ciliate, curved to the left at 

 its anterior extremity ; ventral setae represented by a few scattered styles ; 

 marginal setae forming a continuous projecting fringe, longest towards the 

 posterior extremity ; three only of the anal styles produced beyond the 

 posterior margin. Length 1-168" to 1-144". Hab. — Fresh water. 



Oxytricha platystoma, Ehr. sp. Pl. XLV. Fic-s. 8 and 9. 

 Body elongate, obovate, two and a half times as long as broad, widest 

 towards the anterior extremity, gradually tapering thence to the rounded 

 but narrowest posterior end ; peristome-field deeply excavate, helicoidal 

 not extending to the centre of the body, its reflected inner border curved 

 inwards to the left in a spiral manner, bearing a row of fine pre-oral cilia 

 and an undulating membrane ; ventral sets five in number, maro-inal series 

 forming an uninterrupted, prominent peripheral fringe, two of the anal styles 

 only projecting a slight way beyond the posterior body-margin. 



This species is identical with the Oxytricha platystoma of Ehrenbero- and Stein, 

 The elegant helicoidal contour of the peristome-field distinguishes it from all the 

 preceding species of this genus, and is at the same time so deeply cut as to show 

 clearly through from the dorsal aspect. Diesing * has proposed to separate both this 

 and O. ferruginea from the ordinary Oxytrichcp, and to create for them the new 

 generic title of Steinia ; but in face of the more comprehensive partitionino- of the 

 genus Oxytricha by Wrzesniowski and Sterki, as here adopted, the further^ o-eneric 

 separation of these two types does not at present appear desirable, 



Oxytricha micans, Eng. 

 Body highly contractile ; anal styles slender, eight to ten in number, those 

 towards the right-hand side being largest and most prominent ; shape of the 

 body and disposition of the other styles and setae agreeing with that of 

 Oxytricha pcllionclla. Length 1-300". Hab. — Fresh water. 



Oxytricha seruginosa, Wrz, Pl. XLIV. Figs, 19 and 20. 

 Body very flexible, slightly contractile, elongate-elliptical, about three 

 and a half times as long as broad, the two extremities rounded, the anterior 

 one slightly narrower and curved somewhat to the left; peristome-field 

 extending backwards to a distance of a little over one-fourth of the length 

 of the entire body ; three uncinate frontal styles and three or four frontal 

 setae ; ventral setae five in number, two situated immediately behind the 

 peristome, one central, and the other two adjacent to the anal styles ; anal 

 styles five in number, slender, and not projecting beyond the posterior 



* ' Revision der Prothelminthen,' 1866. 



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