CATHYPNADA. 99 
frontal disk, and when it is extruded, there is an appearance of two lateral, slender, ineurved 
horns, and between them two spots which look like a pair of ill-defined eyes; neither of 
which we see in dunaris. But these are not what they seem: the horns are the optical 
effect of the somewhat thickened and stiffened edges of the extruded head-mass, which, 
in the process of contracting and expanding, incline to each other, resembling conical 
knobs; and the spots are only the summits of certain fleshy eminences, which bear 
vibratile cilia. There is a true eye-spot of large size and crescent form, and of pale-red 
hue, seated on the inner side of the brain-mass, that hangs behind the mastax. 
The ventral plate has its pectoral margin quite straight; it is considerably less than 
the dorsal along each side, while commensurate with it behind. There is a square 
hollow in it for the reception of the foot-bulb, which is somewhat kidney-shaped. The 
toe, viewed vertically, is more blade- than rod-shaped, for the outer margins bulge 
outward in a greater or less degree, the widest part generally (but not invariably) near 
the point. This point has often the semblance of a claw; but this is illusory, for there 
is no true angled shoulder. The trophi are of the normal form, but of unusual length. 
It 1s a very common species, and from its sluggish habits, combined with its minuteness, 
the observer is apt to pass it by with contemptuous neglect.—P.H.G.] 
Length. Of lorica, 5}, inch; total, extended, ;4,5 inch. Habitat. Still waters 
(P.H.G.) : common everywhere. 
M. BULLA, Gosse. 
(Pl. XXV. fig. 4.) v 
Monostyla bulla : : O ; Gosse, Ann. Nat. Hist. 2 Ser. vol. viii., 1851, p. 200. 
[SP. CH. Lorica a pointed oval ; dorsal and ventral plates both gibbous, and nearly 
co-equal ; toe rod-shaped in vertical aspect, with a two-shouldered claw, but decurved and 
gradually tapering in lateral aspect. 
This species I found in a small pool on Hampstead Heath, in August 1850, and, 
soon after, in the lake of Richmond Park, abundant. Lately it has occurred in water 
from Woolston, and from Caversham. The yellow hue is not, as I first supposed, in- 
variable. Some are quite colourless, except for the digesting food. The great rotundity 
of the ventral plate ; the regular decurvation of the tapered toe; and the deep narrow 
sinus in both the occipital and the pectoral fronts of the lorica,—these are the true dis- 
tinctions. The oval outline is so acute in front that the sinuses are bounded only by 
two obtuse points. The gibbous dorsum ends behind with an oblique retrocession, 
showing laterally a great rounded foot-bulb. The head projects in two receding lobes, 
ciliated on their inner surfaces, just as in cornwta. The mallei are certainly two-fingered. 
The animal burrows among Chare, Conferve, &¢.—P.H.G.] 
Length. Expanded, ;}, inch; of lorica, y+; inch. Habitat. Pools (P.H.G.). 
M. Lorpit, Gosse, sp. nov. 
(Pl. XXV.. fig. 5.) 
[SP. CH. Dorsal plate of lorica tesselate, its hinder end excavate, the excavation 
forming three sides of a square ; toe rod-shaped ; claw shouldered. 
This is a rare species, bearing much the same relation as Cathypna rusticula does— 
each to its congeners. Indeed, they are so much alike as to be easily confounded till 
the foot is seen to be two-toed in that case, one-toed in this. It in general resembles 
M. cornuta, but is much more transparent. The single toe is more slender in propor- 
tion to its length, and much longer in proportion to the whole animal; it is a straight 
parallel-sided rod, with a minute acute claw apparently forming a separate joint. If 
this is the case, we should perhaps consider this joint as itself the toe, and the long rod 
as the penultimate joint of the foot. The shoulder is double, viewed vertically, but 
single and much rounded, viewed laterally. The outlines of the toe, however viewed, 
are always a little uneven ; suggesting that the surface is irregularly pitted. The lorica 
H 2 
