538 ORDER HOLOTRICHA. 



Chilodon cucullulus, a second species, which also corresponds closely with this type 

 in its reniform external contour, is easily distinguished from it by the cylinder 

 of rod-like teeth with which the pharynx is armed, and by the unilateral dis- 

 tribution of its cilia. According to Ehrenberg, Colpidium cucullus sometimes pos- 

 sesses two closely approximated contractile vesicles, as well as a double endoplast. 

 It is one of the commonest forms developed in vegetable infusions. 



GENUS VII. PLAGIOPYLA, Stein. 



Animalcules free-swimming, persistent in shape, ovate or subcylindrical, 

 ciliate throughout ; oral fossa ventral, located slightly in advance of the 

 median line, sometimes approached by a transversely directed groove, its 

 inner border bearing a narrow, non-projecting, undulating membrane, fol- 

 lowed by a short tubular pharynx ; anal aperture postero-terminal ; the 

 cortical layer often enclosing trichocysts. 



The enclosure of the undulating membrane within the oral fossa distinguishes this 

 generic type from Colpidium. 



Plagiopyla nasuta, Stein. PL. XXVII. FIGS. 50 AND 51 (?). 



Body subreniform, rounded at each extremity ; oral fossa pocket- 

 shaped, produced at right angles to the cuticular surface to the centre of 

 the body, enclosing an elongate, tongue-shaped, undulating membrane, 

 not followed by a distinct pharyngeal passage ; trichocysts conspicuous ; 

 endoplast elongate-oval, located in the right body-half behind the peri- 

 stome ; contractile vesicle postero-terminal ; anal aperture subterminal. 

 Length 1-240" to 1-190". HAB. Fresh water. 



This typical species of the genus Plagiopyla is described by Stein as somewhat 

 resembling Pleuronema chrysalis, but without the longer ventral cilia or extensile 

 membrane. The animalcule figured by Quennerstedt * under the title of Para- 

 mcecium cucullus, corresponds so nearly with Stein's diagnosis of the present species 

 that the Swedish authority's delineations are herewith reproduced as probably 

 representing the same type. 



Plagiopyla (?) Garten, S. K. PL. XXVI. FIG. 69. 



Body elliptical, cylindrical, equally rounded at the two extremities, 

 about twice as long as broad ; oral aperture situated nearly midway between 

 the centre and the anterior extremity of the body, enclosing a minute, 

 lunate, undulating membrane, followed posteriorly by a conically pointed 

 tubular pharynx ; the anal aperture lateral, situated on the same side as 

 the mouth, midway between the median line and the posterior extremity; 

 cuticular cilia short, disposed in even longitudinal rows ; contractile vesicle 

 lateral, subcentral, located on the opposite side to the oral and anal aspect ; 

 endoplast undetermined. Length 1-125". 



HAB. Fresh water : Bombay (H. J. C). 



* 'Sveriges Infusoriefauna,' 1867. 



