114 Transactions. — Zoology. 



were observed only once in B. macrurics, and then they were 

 very indistinct. Far back, within the contour of the body, 

 are the trophi. These are of the same shape as those of 

 M. macrurus, but instead of having only two they have four 

 distinctly marked transverse ridges. The stomach is very 

 capacious. No brain was observed ; neither was any kind of 

 sense-organ. The eyes and the dorsal organ are entirely 

 wanting. 



Movement, quite like that of other Phillodinidans. 



Hab. The horse-trough. 



I found only one specimen of this species, and so my de- 

 scription is lamentably incomplete ; but there is no doubt that 

 it is a species quite distinct from C. bidens, which in general 

 aspect it somewhat resembles. 



Order PLOIMA. 



Sub-order IL-LORICATA. 



Family Hydatinad^. 



Genus Hydatina, Ehrenberg. 



Generic characteristics : Body conical, tapering towards 

 the foot. Foot short, and confluent with the trutik. Eye 

 absent, or one cervical. 



The distinctive characters of this genus have been en- 

 larged by me, so as to admit a specimen clearly very closely 

 allied to H. senta, but possessing a large complex and beauti- 

 ful eye. 



III. Hydatina monoids, sp. nov. Plate VIII. , fig. iii. 



Specific characters : Brain large, dark, and very noticeable. 

 It is composed of two large lateral lobes and a smaller pos- 

 terior one, which is balanced in front by a large red eye. 



One of the three largest Eotifers I have seen, equalling 

 Planoventer gigans and Notomviata pentophthalma. There is 

 no definite colour excepting that of the eye, but. the usual 

 transparency is absent here, owing partly to its great bitlk, 

 and also, no doubt, to a greyish tinge in the organs them- 

 selves. The whole animal is pisciform, although it does not 

 taper towards the head. The body is cylindrical, and tapers 

 posteriorly to the thick short foot, which ends in the two 

 small toes. The head is marked off from the body by a deep 

 indented line or neck ; it leaves the head about one-third the 

 length of the body, and almost as great in circumference. The 

 head is truncated in front, so that the corona is transverse. 

 The cilia are disposed in a single row, fringing the head of the 

 corona, but breaking opposite the mouth. The cilia at the 

 sides of the head are very large. Several large tufts of cilia 



