540 ORDER HOLOTRICHA. 



two in number, of large size, assuming at full diastole a stellate contour, 

 situated in the same median line towards the anterior and posterior regions 

 of the body ; endoplast elongate-ovate, longitudinally disposed, located a 

 little to the rear of the oral fossa. Length 1-288" to 1-180". 

 HAB. Fresh water. 



This species was first figured and described by Eckhard * under the name of 

 Paramcecium stomioptycha, and has been referred to later on by Ehrenberg \ in 

 connection with the same title. Although the surface ciliation and character of the 

 contractile vesicles accord closely with those of certain Paramcecia, the oral 

 structure, as delineated in Eckhard's original drawing, herewith reproduced, is 

 essentially distinct. 



GENUS IX. CHASMATOSTOMA, Engelmann. 



Animalcules free-swimming, persistent in shape, ovate or kidney-shaped, 

 somewhat flattened ; cilia long, matted, equally distributed ; oral fossa 

 situated near the centre of the flattened ventral surface, enclosing a minute 

 undulating membrane. 



While the contour of the body, the matted character of the cilia, and the position 

 of the oral fossa in this genus correspond closely with those of Conchophthirus , the 

 possession of a supplementary undulating membrane indicates its affinity with 

 Ophryoglena and Meniscostomum. 



Chasmatostoma reniforme, Eng. PL. XXVI. FIG. 48. 



Body kidney-shaped, about one and a half times as long as broad, 

 obtusely rounded at each extremity, the anterior one slightly the narrower, 

 the dorsal surface convex, the ventral one flattened ; oral fossa subcentral, 

 small, and of ovate contour ; undulating membrane attached to the right 

 inner side of the oral cavity ; cilia long, fine, and thickly set over the entire 

 cuticular surface, presenting a tufted or matted aspect ; contractile vesicle 

 postero-terminal, rosette-like during systole ; endoplast spherical, situated 

 in front of the contractile vesicle. Length 1-400". 



HAB. Fresh water, with Colpoda cucullus, 



This species is figured and described by T. W. Engelmann in the ' Zeitschrift fur 

 Wissenschaftliche Zoologie,' Bd. ii., for the year 1862. 



GENUS X. PLEUROCHILIDIUM, Stein. 



Animalcules free-swimming, persistent in shape, not encuirassed, sub- 

 reniform and flattened, entirely ciliate ; oral fossa antero-ventral, ear-shaped, 

 having attached to its right margin a narrow undulating membrane ; tricho- 

 cysts often present. 



This and the following genus, Ptychostomum, were instituted by Stein in the 

 ' Bohmischen Sitzungsbericht,' Bd. ii., for the year 1860. Unfortunately, no figures 

 of either of the several specific forms referred to these genera have as yet been 

 published. 



* 'Wieg. Archiv,' p. 219, Taf. vii. fig. 4, 1846. 

 t 'Bericht Akad. Berlin,' 1853. 



