GENUS MENISCOSTOMUM. 539 



This species, figured and briefly described by Mr. H. J. Carter in his manuscript 

 notes under the title of FaramcEciujJi ?, as also the form next described, would perhaps 

 be more rightly referred to the genus Ophryoglena, though in all essential details, 

 with the exception of the transverse groove-like approach to the oral aperture, it 

 would seem to conform with Stein's diagnosis. While no mention is made of the 

 lunate vibratile membrane within the oral fossa, its presence is clearly indicated in 

 Mr. Carter's sketch as here reproduced. The backward continuation of the 

 pharyngeal cleft beyond the attachment of the enclosed vibratile membrane, both in 

 this and the succeeding species, in addition to the smaller size and more ventral 

 location of the oral aperture, distinguishes them from the ordinary members of the 

 genus Ophryoglena. 



Plagiopyla (P) fusca, Quenn. sp. Pl. XXVI. Fig. 70. 



Body persistent in shape, elliptical, evenly rounded at each extremity, 

 twice as long as broad ; cuticular surface delicately striate longitudinally, 

 finely ciliate throughout, the cortical layer enclosing closely set trichocysts ; 

 oral aperture opening a little in advance of the median line, enclosing 

 a conspicuous undulating membrane, followed by a short, backward directed, 

 tubular pharynx; contractile vesicles two in number, small, spheroidal, 

 one stationed in the anterior, and the other in the posterior third of the 

 body; endoplast oval, subcentral. Length 1-200". Hab. — Saltwater. 



This animalcule is figured and described in connection with the above specific 

 name, by Quennerstedt * as a new form of Pmiophrys ; the non-existence, however, 

 of a fringe of larger cilia round the oral aperture necessitates its removal from that 

 genus, while the construction of the oral aperture and pharyngeal passage indicates 

 its close affinity with the type last described. 



Genus VIII. MENISCOSTOMUM, S. K. 



Animalcules free-swimming, ovate, persistent in shape, entirely ciliate; 

 oral fossa lateral, shallow, meniscoidal, enclosing a narrow, lunate, vibratile 

 membrane, no cilia of larger size round its outer border, and not followed 

 by a tubular pharynx ; contractile vesicles usually two in number. 



This new generic appellation is here instituted for the reception of a single 

 Holotrichous type whose form and structure, while most closely approaching that of 

 the preceding genera Ophryoglena and Plagiopyla, differs from the former in the 

 simple cup-like contour of the oral fossa, and from the latter by the absence of 

 an accompanying tubular pharyngeal passage. The cup-like oral fossa, as seen in 

 profile, presents a very characteristic aspect, appearing under such conditions as 

 a clean-cut lunate notch in the antero-lateral border, as shown in the figure illustrative 

 of the single type described. 



MenisGOstomum stomioptycha, Eck. sp. Pl. XXVII. Fig. 48. 



Body obtusely ovate or elliptical, evenly rounded at both extremities, 

 about twice as long as broad ; oral fossa forming a shallow circular exca- 

 vation at a distance of one-third of the entire length of the body from the 

 anterior extremity, its inner border bearing a lunate vibratile membrane; 

 cuticular cilia even, forming dense longitudinal series ; contractile vesicles 



* ' Sveriges Infusoriefauna,' 1869. 



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