GENUS PLEUROTRICHA. 78 1 



Uroleptus violaceus, Stein. Pl. XLIII. Fig. 18. 



Body persistent in shape, broadly linear, flattened, five to six times as long 

 as broad ; the anterior extremity widest, truncate, its corners rounded, 

 gradually tapering towards the truncate and rounded posterior end, the 

 width of which, at its termination, is equal to nearly half that of the 

 anterior one ; peristome-field developed backwards to about one-fifth of the 

 length of the body, its reflected border arcuate, unciliate ; marginal setae 

 projecting beyond the periphery, lengthening as they approach the pos- 

 terior extremity ; median rows of ventral setae two in number, produced 

 nearly to the extremity of the tail-like termination ; position of contractile 

 vesicle and endoplasts similar to that of U. ratulus ; the parenchyma 

 usually enclosing numerous brilliant violet granules. Length 1-160" to 

 i-ioo". Hab. — Fresh water. 



Uroleptus mobilis, Eng. Pl. XLIII. Figs. 9 and 10. 



Body flexible, elongate-linear, cylindrical, about twelve times as long as 

 broad, attenuate posteriorly and terminating in an abruptly truncate point ; 

 peristome exceedingly narrow, extending backwards to about one-ninth of 

 the length of the entire body, its inner or reflected border bearing an undu- 

 lating membrane ; frontal styles uncinate, three in number ; ventral setae 

 undescribed ; marginal setae long, fine, and evenly developed, but widely 

 separated ; contractile vesicle situated at a distance of one-third of the length 

 of the body from the anterior extremity ; endoplasts elongate oval, six 

 in number. Length 1-75". Hab. — Fresh water. 



This species may be distinguished from U. ratulus by the abruptly truncate contour 

 of the tail-like posterior extremity, the longer and more scattered marginal setae, and 

 by the comparatively shorter peristome-field. 



Uroleptus agilis, Eng. 



Body flexible but persistent in form, elongate-lanceolate, four or five 

 times as long as broad, widest centrally, tapering to the two extremities, 

 the posterior one slightly the narrower ; peristome-field moderately wide, 

 extending backwards to a distance of about one-fifth of the length of the 

 body ; frontal styles four in number, bearing immediately behind them 

 three antero-ventral setae, a few additional ventral setae developed in the 

 centre of the body ; marginal setffi set far inwards, projecting beyond the 

 periphery only at the posterior extremity of the body, the hindermost setae 

 of this series much larger than the preceding, forming a terminal projecting 

 fascicle ; contractile vesicle situated near the centre of the left lateral border j 

 endoplasts elongate-ovate, two in number. Length 1-300" to i-ioo". 



Hab. — Fresh water. 



As remarked by Engelmann,* this species intimately connects the two genera 



» 'Zeit. Wiss. Zool.,' Bd. xi., 1861. 



