COLURID^E. 108 



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 rising 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 Button Park, Birmingham. Its manners 

 are peculiar. It swims constantly, never resting to grope, as other species do, but sail- 

 ing deviously 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.J 



Length. Extended, -^ inch ; transverse width ^^. Habitat. Woolston ; Birming- 

 ham (P.H.G.) ; very rare. 



C. UNCINATUS, Ehrenberg. 

 Colurus uncinatus . . . Ehrenberg, Die In/us. 1838, p. 475, Taf. lix. fig. 6. 



[SP. CH. Lorica, viewed dorsally, broadly ovate, truncate before, produced behind 

 into two short spines : vieived laterally, the outline 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 Euchlanis deflexa], 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 denned. It is usually of minute dimensions, and, though 

 widely spread, rather rare. I have known it since 1849. P.H.G.] 



Length. Lorica, from ^^ to ^ inch. Habitat. Clapton ; Battersea ; Bath ; 

 (P.H.G.). 



C. OBTUSUS, 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 fissure reach- 

 ing round 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 setae 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 011 the brain, which may be eyes. Its 

 manners are sluggish, swimming laboriously, with jerks. P.H.G.] 



Length. Without foot, r ^ to ^^ inch. Habitat. Near London ; Woolston ; Lea- 

 mington ; Dundee (P.H.G.) : not uncommon. 



