CATHYPNADJE. 99 



frontal disk, and when it is extruded, there is an appearance of two lateral, slender, incurved 

 horns, and between them two spots which look like a pair of ill-defined eyes ; neither of 

 which we see in hmaris. 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 is a very common species, arid 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, ^^ inch; total, extended, T ^ inch. Habitat. Still waters 

 (P.H.G.) : common everywhere. 



M. BULLA, Gosse. 



(PI. XXV. fig. 4.) 



Monostyla bulla .... Gosse, Ann, Nat. Hist. 2 Ser. vol. viii., 1851, p. 200. 



[SP. CH. Lorica a pointed oval ; dorsal and ventral plates loth 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 Eichmoiid 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 decurvatioii 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 cornuta. The mallei are certainly two-fingered. 

 The animal burrows among Chane, Conferva?, &c. P.H.G.] 



Length. Expanded, T | 5 inch ; of lorica, T |- inch. Habitat. Pools (P.H.G-.). 



M. LORDII, Gosse, sp. nov. 

 (PI. XXV. fig. 5.) 



[SP. CH. Dorsal plate o/ lorica tesselate, its hinder end excavate, the excavation 

 forming three sides of a square ; toe rod-sliaped ; claw shouldered. , 



This is a rare species, bearing much the same relation as Cathy pna 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 cormita, 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 jomt of the foot. The shoulder is double, viewed vertically, but 

 single and much rounded, viewed laterally. The outlines of the too, however viewed, 

 are always a little uneven ; suggesting that the surface is irregularly pitted. The lorica 



ii 2 



