COLURID. 103 
and what appears a single, slender, acute toe. At least I could not, with close watching, 
detect any sign of its division. In the dorsal view the frontal hood (fig. 2) appears not 
as the segment of a sphere, but somewhat indented in front. It ever moves backward 
and forward, as protruded and retracted. The venter appears quite flat, the semi-globose 
dorsal plate rismg abruptly from it with a sharp angle. In one, as it turned slowly, I 
saw distinctly the form. If we suppose one-third of an egg to be removed longitudinally, 
and replaced by a flat plate, we shall gain a fair idea of the general outline. 
This is certainly an uncommon form. My acquaintance with it is limited to a very 
few examples, obtained from Woolston Pond, and Sutton Park, Birmingham. Its manners 
are peculiar. It swims constantly, never resting to grope, as other species do, but sail- 
ing deyiously and deliberately about; now and then quickening its pace; almost con- 
stantly with the venter at the glass of the cell; so that whereas I obtained plenty of 
ventral views, I got few dorsal, and scarcely one good lateral.—P.H.G.] 
Length. Extended, ;1, inch; transverse width ;3,;. Habitat. Woolston; Birming- 
ham (P.H.G.) ; very rare. 
C. uncinatus, Ehrenberg. 
Colurus uncinatus 7 5 0 Ehrenberg, Die Infus. 1838, p. 475, Taf. lix. fig. 6. 
[SP. CH. Lorica, viewed dorsally, broadly ovate, truncate before, produced behind 
into two short spines: viewed laterally, the owtline is rondo-triangular, high in the 
middle of the back, the posterior spines short, blunt, and abruptly set-on ; venter widely 
cleft throughout; toes two, short, slender, acute. Lacustrine. 
The lorica is turgid, the back not ridged but smoothly rounded; its ventral gape 
parallel-edged, the edges apparently bent downward (as in Huchlanis deflera), making 
an angle with the swell of the sides, the anterior portion lengthened into a short tubular 
neck. The hook is narrow and spoon-shaped. The internal structure is obscure, partly 
from its sphericity; yet the mastax, stomach, intestine and cloaca, the ovary and 
the contractile vesicle, can be defined. It is usually of minute dimensions, and, though 
widely spread, rather rare. I have known it since 1849.—P.H.G.] 
Length. Lorica, from 5}, to zy}, inch. Habitat. Clapton; Battersea; Bath; 
(P.H.G.). 
C. optusus, Gosse, sp. nov. 
(Pl. XXVI. fig. 3.) 
[SP. CH. Lorica ovate in all aspects, the posterior ends rounded without any points, 
ventrally cleft throughout, gradually expanding for the foot-orifice, the fisswre reach- 
ing rownd to the back, both before and behind ; foot small, with two minute slender, ex- 
panding toes. Lacustrine. 
This little unrecognised species, which I find not uncommon, is clearly marked by 
the blunt ends of the lorica. The lateral plates are separate for above three-fourths of 
their circumference, being soldered together with a sharp suture, only in the very middle 
of the back, and generally much compressed. The foot and toes together are about one- 
third as long as the lorica; the toes, like sete for tenuity, with no shoulder, are often 
separate. The internal economy is normal ; including the common bubbles in the back ; 
two colourless refractile globules have been seen on the brain, which may be eyes. Its 
manners are sluggish, swimming laboriously, with jerks.—P.H.G.] 
Length. Without foot, =, to 34; inch. Habitat. Near London; Woolston; Lea- 
mington ; Dundee (P.H.G.): not uncommon. 
