784 ORDER HYPOTRICHA. 



marginal setae forming a continuous border, usually longest posteriorly ; 

 peristome-border reflected, bearing an undulating membrane ; endoplasts 

 two or four in number. 



This genus, as established by Engelmann,* is to be distinguished from Pleuro- 

 tricha by the single oblique series of ventral styles, which here takes the place of the 

 several supplementary rows that characterize the last-named genus. 



Gastrostyla Steinii, Eng. Pl. XLIII. Fig. 16. 



Body elliptical, rounded at each extremity, slightly widest posteriorly, 

 nearly three times as long as broad ; peristome-field extending backwards 

 to a distance of about one-third of the length of the entire body, its reflected 

 border bearing a conspicuous undulating membrane ; frontal styles six in 

 number ; about three scattered ventral styles developed in addition to 

 the oblique linear series ; anal styles four or five, forming a single oblique 

 row, not projecting beyond the posterior extremity ; marginal setae coarse, 

 increasing in length as they approach the hinder extremity of the body ; 

 contractile vesicle situate close to the posterior angle of the peristome; 

 endoplasts ovate, four in number, arranged in a line down the centre of 

 the body, each with a minute laterally attached endoplastule. Length 

 1-150" to 1-75". Hab. — Fresh water. 



Gastrostyla setifera, Eng. sp. 



Body elongate lanceolate, slightly gibbous, widest centrally, equally 

 narrowed at the two extremities, about two and a half times as long as 

 broad ; peristome-field extending backwards nearly to the centre of the 

 body, its reflected border bearing a band-like undulating membrane, and its 

 central area supplemented by a conspicuous median line of endoral cilia ; 

 frontal styles five in number, uncinate, the three anterior being the largest ; an 

 oblique row of central and a few scattered ventral styles ; anal styles five in 

 number, forming two groups of three and two each, the latter only projecting 

 beyond the posterior border; marginal setae coarse, longest posteriorly; 

 contractile vesicle situated near the centre of the left-hand lateral border ; 

 endoplasts two in number, ovate. Length 1-80". Hab. — Fresh water. 



This species has been described by Engelmann under the title of Pleurotricha 

 setifera, but, as shown by his illustration, the character and arrangement of the 

 ventral styles coincide so completely with those of Gastrostyla Steinii, that it 

 appears desirable to refer it to the same genus. The four or five additional frontal 

 set^ mentioned by Engelmann would appear to correspond with the anterior setae of 

 the oblique ventral row, as none separate from these are exhibited in his drawing, 

 while at the same time the oblique row is not referred to in the text, the ventral 

 styles being described merely as five or six in number. Diesing,t premising that 

 there is a separate group of frontal setae, in addition to the five uncinate styles and 

 oblique ventral row, has proposed for this type the new generic title of 

 Nothopleurotricha. 



Sterki % intimates that he has encountered two new large-sized species 



* ' Zeitschrift fiir Wissenschaftliche Zoologie,' Bd. xi., i86i. 



t ' Revision der Prothelminthen,' 1866. 



X 'Zeitschrift fur Wissenschaftliche Zoologie,' Bd. xxxi., 187S. 



