38 THE EOTIFEltA. 



liave seen the saccate brain at its hinder end, densely opaque in a great ball, just as in 

 N. atirita, while all the remainder was clear. In every other respect the specimen was 

 a normal sordida. The most obsei"vable characteristic of this species, by which it may 

 without fail be identified (for it is quite constant), is the condition of the foot. The 

 hinder half of the trunk, viewed dorsally, insensibly diminishes to a width about one- 

 third that of the widest part, where it is abruptly truncate ; the hind half of this is 

 separated by a slight fold, and appears to constitute the foot-proper. Yet there are no 

 visible joints in it, and its outline, as I have said, simply continues the gradual tapering. 

 Down the middle of this foot there runs what seems a shallow depression, crossed by 

 two similarly depressed transverse lines, and the whole ends in two small conical toes. 

 When once this peculiarity has been noticed, there is no mistaking it. 



I first found the species in a tube sent me by Mr. Hood from Dundee, and since 

 then in water from Miss Saunders of Cheltenham, and abundantly from Woolston, 

 sent by Miss Davies. Some of these last were hyaline, and more active. — P.H.G.] 



Length, , \ ,7 to yi^^y inch. Habitat. Many localities in England and Scotland : 

 common in pools (P.H.G.). / ^S -^30/^ 



P. TiGRiDiA, Gome, sp. nov. 

 (PI. XVIII. fig. 10.) 



[SP. CH. Body cylindric or f uniform, curved in the manner of Kattulus ; foot 

 and toes holli long, and bent in a sigmoid curve. 



This animal, I do not doubt, has been confounded by observers, as it was by myself, 

 with the A'', tigris of Ehrenberg, but this latter I now relegate to another genus, in the 

 Sub-order Loeicata. The present is certainly il-loricate, and its long ciliate face, 

 almost absolutely prone, shows its aifinities to be here, though it is certainly osculant 

 with Battulus. Its trophi, too, are symmetrical, and of the Notommatous pattern. 

 The cilia of the face seem set on minute eminences ; and there are longer setse among 

 them. The belly line bends upward and then downward to hiclude the base of the deep 

 foot, which again bends upward (i.e. backward) to the toes, and these bend downward 

 at their tips. So that the whole line from the face to the toe-tips forms a double 

 sigmoid curve of much elegance. In June 1885 I first became cognizant of this interesting 

 form. It was haunting the decaying whorls of Nitella, in water from Woolston Pond, sent 

 me by the kind courtesy of Miss Saunders. It has occurred also in other waters. 



It is an energetic animal, given to sudden and rapid changes of motion, shooting 

 tln-ough the free water with great celerity, the toes stretching behind straight and 

 parallel ; now abruptly turning on itself to pursue another course, now arrested by a 

 cloud of floccose, to dig into the decaying vegetation with apparent determination and 

 vigorous perseverance. The digestive canal is almost invariably dark with granular 

 food, of a deep rich-brown hue. A contractile vesicle is usually conspicuous. - P.H.G.] 



Length, -[I J inch. Habitat. South and Midland England ; pools (P.H.G.) : rare. 



P. rETKOMYZON, Ehrenberg. 

 (PI. XVIII. fig. n.) 



Kotommain petro>nysL)ii . . . . Ehrenberg, Die /«/us. p. 427, Taf. 1. fig. 7. 



[SP. C'll. Body ovale ; foot long, stout, and very distinct ; toes minute. 



The form is gibbous-ovate, truncate at each extremity, when contracted ; the head is 

 roimded, protrusile ; the foot apparently of one joint, very large and long, but abruptly 

 less in width than the truncate body whence it issues ; the two toes are very minute 

 cones. The character of the foot makes the species particularly easy of recognition. 



The sii-.i]3licity of the trophi make's them very instructive. The incus-fulcrum is 



