106 THE ROTIFEBA. 



currents in the water, and so to examine its appearance in other aspects. Thus was this 

 creature delineated, and I vouch for its accuracy so far as the details are given. 



The lorica seems (I can say no more) to be widely severed on the ventral aspect, and 

 to end in rectangular points behind. The frontal hook appears normal. P.H.G.] 



Length, to tip of spine, T J ^ inch ; of which the spine is about one-fourth. Habitat- 

 Among conferva in tide-pools in the Firth of Tay (P.H.G.) ; rare. 



Genus METOPIDIA, Ehrcnbcrg. 



[GEN. CH. Lorica usually depressed, entire, with an opening at each end for the 

 emission of the head and foot ; frontal hood in form of a liook ; foot and toes as in 

 Colurus ; eyes usually tico. 



For reasons already given I include in this genus, not only the species so named by 

 Ehrenberg, but also his genera Lepadella and Squamella ; thus agreeing in principle 

 with Dujardin (" Infus." p. 632) while I cannot accept his details. They seem to fall 

 into the same natural family as Colurus ; for though the prevailing plate-like form seems 

 at first sight to differ greatly from the compressed Coluri, yet this form is not invariable, 

 M. oxysternum and M. triptera presenting notable exceptions ; while in the arched 

 frontal hook there is a remarkably conspicuous feature in common. Some of the species 

 are among the most familiar of Eotifera. P.H.G.] 



M. LEPADELLA, Ehrenberg. 

 (PI. XXV. fig. 6.) 



Melopidia lepadclla . . . Ehrenberg, Die Infus. 1838, p. 477, pi. lix. fig 10. 



[SP. CH. Lorica oval, much depressed, evenly rounded above ; its ventral plate 

 shorter behind than the dorsal, and slightly excavate. 



That Ehrenberg's Lepadella ovalis, Squamella bractea&nd S. oblonga, and Metopidia 

 lepadclla are but species of one genus, I cannot doubt, and even the specific differences 

 between them are very evanescent. The number, and even the visibility, of the eye-specks 

 vary in individuals, and cannot be trusted for diagnosis. The present is a common form 

 in most fresh waters. The lorica in its dorsal outline, both longitudinal and transverse, is 

 a segment of a circle, and the ventral is straight. Seen from above it is oval, pointed 

 at both ends, and yet truncate ; the ventral plate round behind, and so considerably shorter > 

 and slightly emarginate for the emission of the foot. The frontal hood agrees with 

 that in Colurus, slightly protrusile, and is used for raking the rubbish among which it 

 feeds. The ciliate face is almost prone, and the trophi can be brought to its surface. 



I think I have seen the male ; a minute creature, in form a very long cone, tapering 

 to a point, with two slender toes ; in front, quite truncate, with a sharp horn projecting 

 from its forehead. No organization was visible within, save two conspicuous clear vesicles, 

 side by side in the middle of the body, not at all like oil-globules, being irregularly 

 oblong : nor accidental, being found in each of a large number of individuals, seen at 

 different times. A pair of fine lines ran far down the two sides of the body, and in the 

 hinder part was a large angular web of thin yellowish tissue. Else the whole seemed 

 structureless and of hyaline clearness. It contracted into a shorter oval figure. P.H.G.] 



Length. Of lorica, 3-'-^ inch. Habitat. Fresh waters everywhere (P.H.G.). 



M. SOLIDUS, Gossc. 

 (PI. XXV. fig. 11.) 



Metopidia solidus .... Gossc, Ann. Nat. Hist. 2 Ser. vol. viii. 1851, p. 201. 



[SP. CH. Lorica nearly circular, depressed, with a low rounded ridge above ; 

 ventral plate commensurate u-ith the dorsal behind, but deeply excavate ; dorsal having 

 a submarginal line of corrugation. 



