750 ORDER HYPOTRICHA. 



Opisthodon niemeccensis, Stein. PL. XLII. FIG. 23. 



Body elongate-ovate, rounded and widest posteriorly, attenuated and 

 pointed at the anterior extremity, its apex curved slightly towards the 

 right; the centre of the body circumscribed by an inner line or band 

 parallel with that of the outer margin; the dorsal surface moderately 

 convex, the ventral one flat and even ; cilia most conspicuously developed 

 towards the anterior region ; the oral aperture opening at a distance of 

 about one-quarter the length of the entire body from the rounded posterior 

 end ; endoplasts two in number, spherical, located centrally towards the 

 left side ; contractile vesicles numerous, a larger one usually situated 

 on the right side, immediately opposite 4he two endoplasts. Length of 

 body i-i 50". HAB. Fresh water. 



GENUS V. CHLAMYDODON, Ehrenberg. 



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

 the dorsal surface convex, the ventral one plane, bounded by a raised border, 

 its central area alone entirely ciliate ; oral aperture situated in the anterior 

 half of the body, supplemented by a pharyngeal rod-fascicle. 



Chlamydodon Mnemosyne, Ehr. PL. XLII. FIGS. 41 AND 42. 



Body short, kidney-shaped, the two extremities equally rounded, the 

 anterior end somewhat the wider, both curved slightly towards the left ; the 

 dorsal surface convex, its lateral margin evenly elevated ; the ventral sur- 

 face bounded by a raised, transversely striate border ; cilia most conspicuous 

 at the anterior extremity, whence they project as a fringe beyond the 

 margin of the body ; mouth debouching upon the centre of the anterior body- 

 half ; endoplast single, ovate, subcentral ; contractile vesicles numerous, 

 minute ; dividing by transverse fission. Length of body 1-300". 



HAB. Salt water. 



GENUS VI. SCAPHIDIODON, Stein. 



Animalcules free-swimming, scaphoid or boat-shaped, convex above, 

 flattened below ; the posterior extremity produced in a beak- or spur-like 

 form, the anterior edge having a lip-like border; the centre field of the 

 ventral surface thickly ciliate ; oral aperture anteriorly situated, supple- 

 mented with a pharyngeal rod-fascicle. HAB. Salt water. 



Scaphidiodon navicula, Miiller sp. PL. XLII. FIGS. 49 AND 50. 



Body boat-shaped, the breadth equal to about one-third of the total 

 length ; the anterior margin truncate, the posterior region attenuate, con- 

 tinued in a spur-like form, with its extremity curved towards the left; 

 the ciliary system of the ventral surface produced in a fringe-like manner 

 beyond the truncate anterior margin ; endoplast central, oval ; contractile 



