GENUS STYLONYCHIA. 791 



field occupying the entire left side of the anterior ventral surface, its 

 reflected inner border ciliate and supporting a conspicuous, band-like, 

 undulating membrane ; the two right-side anal styles projecting beyond 

 the posterior extremity ; three long, widely separated, caudal setae springing 

 from the truncate posterior end, in which region the otherwise even and 

 prominently developed marginal series is considerably interrupted ; both 

 the anal and frontal styles occasionally fibrillate or branched at their 

 extremity. Length 1-280" to 1-72". 



HAB. Fresh water ; also abundant in infusions. 



Sterki alludes briefly in his ' Morphologic der Oxytrichinen ' * to a variety of 

 this animalcule, upon which he confers the sub-specific name Stylonychia mytilus van 

 pusilla. The caudal setae in this modified type attain the length of one-half of the 

 body, and are either bi- or tri-furcate at their free extremities ; there are but from 

 twelve to eighteen marginal setae on the right, and from ten to fourteen only on the 

 left-hand lateral border, while the lengths of the larger examples range from 1-275" 

 to 1-200". 



Stylonychia pustulata, Ehr. PL. XLV. FIGS. 15-17. 



Body elongate-ovate, equally wide in front of and behind the median 

 line, the posterior extremity evenly rounded, bearing three long, closely 

 approximated caudal setae which scarcely interrupt the marginal series ; 

 three or four of the anal styles projecting beyond the posterior border ; 

 endoplasts oval. Length 1-280" to 1-120". 



HAB. Salt, fresh, and stagnant water. 



This animalcule is common in infusions, and may be distinguished from the 

 preceding type, in addition to its smaller size, by its rounded posterior extremity, by 

 its more closely approximated caudal setae, and by the more numerously projecting 

 anal styles. 



Stylonychia fissiseta, C. & L. PL. XLV. FIG. 22. 



Form and dimensions of the body identical with those of S. pustulata ; 

 marginal setae fewer, larger, wider apart, and not projecting beyond the 

 peripheral border ; each of the five anal styles feather-like or fibrillate at 

 their distal extremity ; three very long, widely separated caudal setae, 

 branched in a trifid manner at their free end, projecting from the posterior 

 extremity. 



HAB. Fresh water : Berlin Zoological Gardens (C. & L.). 



The illustration given by Claparede and Lachmann, here reproduced, represents 

 eleven anterior or frontal uncini, while their description testifies to only eight, the 

 normal number associated with this genus. The elegant branched or fimbriate 

 character of the anal styles in a manner resembling the feathering of an arrow, and 

 trifurcation of the caudal setae, as also the non-prominence of the marginal setae 

 serve to distinguish it readily from either of the preceding forms. 



x Stylonychia macrostyla, Sterki. 



Corresponding closely with S. mytilus, more or less flexible, rounded 

 anteriorly, the posterior margin broadest and truncate ; all the styles and 



* ' Zeitschrift fur Wissenschaftliche Zoologie,' 1878. 



