16 Transactions. — Zoology. 



Cyclidium or Pleuronema (Holotrichous) in being never retracted 

 and always vibrating. The absence of a pharyngeal tube, or of 

 a distinct peristome-field, is another character separating the 

 genus from other Hypotricha. 



Thurophora lucens, sp. nov. Plate IV., fig. 26, a, b, c, d. 



Animalcules free-swimming, encuirassed, sub-elliptical when 

 viewed dorsally or ventrally. Colour white, very translucent ; 

 cuirass indurated ; cuticular surface distinctly striated ; in side 

 view elongate, narrow, truncate anteriorly, more or less pointed 

 posteriorly ; in end view from the anterior extremity convex 

 above, deeply concave below, the edges incurved. Oral region 

 occuying about three-fourths of the length, ventrally ; elliptical, 

 partly closed by a membranous, vibratile process, free on one 

 side and apparently hinged all along the other. At the anterior 

 extremity the oral region forms a very narrow groove, the sides 

 of which are produced in two very short pointed processes bear- 

 ing a bunch of short seta? ; one of these processes is longer than 

 the other. The membranous valve, or door, is very transparent 

 and difficult to observe ; but in the side and end views it may 

 be seen projecting ; it appears to bear on its edge some short 

 cilia. 



The body bears cilia throughout ; but the dorsal cilia are 

 very short, and seem to have no locomotive action ; those of the 

 ventral surface are longer and vibratile. The motion of the 

 animalcules is very rapid, gliding, with occasional leaps. 



Contractile vesicle single, central, appearing behind the oral 

 membrane when the animalcule is viewed ventrally. Nucleus 

 elongate, irregular, sub-central, rather nearer to the posterior 

 end. 



In several specimens observed a bundle of rather long, very 

 fine cilia or setae appeared at the posterior extremity, as shown 

 in fig. 26, a. These were only to be made out in certain lights, 

 and were not rendered conspicuous even by treatment with 

 osmic acid, iodine, or other re-agents. As the animalcules 

 exhibiting them presented no features distinctive from the others 

 it was not thought advisable to make two species of them. 



Length, T ^ inch = 62-5 p ; width, ^ T) inch = 43*7 /u. 



Masterton, Otaki, Kaitoki, IT. M. Maskell. 



This animalcule, which seems fairly common in the localities 

 named, does not agree with any hitherto described. Its rapid 

 motion and very translucent appearance render it extremely 

 difficult to examine it properly. The membranous appendage, 

 as mentioned above, differs essentially from that of the Holo- 

 trichous Cyclidium or Pleuronema. 



Genus Kerona. 

 Kerona polygonum, Elnenb. On Hydra, Waiwetu, 



