106 THE ROTIFERA. 
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, +} inch; of which the spine is about one-fourth. Habitat. 
Among conferve in tide-pools in the Firth of Tay (P.H.G.); rare. 

Genus METOPIDIA, Ehrenberg. 
[GEN. CH. Lorica wswally depressed, entire, with an opening at each end for the 
emission of the head and foot; frontal hood in form of a hook ; foot and toes as in 
Colurus ; eyes usually two. 
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 Colwrus; 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 Rotifera.—P.H.G.] 
M. LEPADELLA, Hhrenberg. 
(Pl. XXV. fig. 6.) 
Metopidia lepadella 6 C ; Ehrenberg, Die Infus. 1838, p. 477, pl. 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 and S. oblonga, and Metopidia 
lepadella 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 Colwrus, 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, 5}, inch. Habitat. Fresh waters everywhere (P.H.G.). 
M. sourpus, Gosse. 
(Pl. XXY. fig. 11.) 
Metopidia solidus 4 * , : Gosse, 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 with the dorsal behind, but deeply excavate ; dorsal having 
a submarginal line of corrugation. 
