and tSpecies of MoUusca. 317 



one sixteenth of an inch in width, linear, parallel-sided, nearly 

 opaque, of an olive-colour, much paler beneath. An internal 

 mass seen through the skin and flesh, between the first 

 branchiae, most conspicuous in the lateral view (a), of a rich 

 brown hue, is doubtless the liver. The whole upper surface 

 is clothed, more especially toward the posterior portion, with 

 a transparent skin, nearly colourless under transmitted, but of 

 a light bluish-green hue under reflected light. This enve- 

 lops the dorsal tentacle-sheaths and the exterior of the 

 branchial leaves, and forms a loose web in the angles caused 

 by the projection of these organs, and gathers in loose irregular 

 folds over the ridge on each side from which they spring;. 

 This membrane is everywhere studded with subconical tuber- 

 cles of denser substance. The under parts are destitute of 

 this membrane. 



Oral tentacles (c) large and conspicuous, each terminating 

 in a conical process, whose flat bottom is applied to the ground 

 in crawling, and from whose edge radiate three or four long 

 fingers, alternating with as many rudimentary ones, the w^hole 

 bearing a striking resemblance to the foot of a triton or frog. 

 These hands of outstretched fingers are constantly used, in 

 crawling, to feel the way : the fingers contract suddenly, in 

 various degrees, every instant ; and by their movements it is 

 indubitably seen that these tentacles are very sensitive organs 

 of touch. 



Uorsal tentacles proceeding from the shallow trumpet-like 

 extremities of large erect sheaths (t?), which are thick, colum- 

 nar, and very mobile. The sheaths are composed of the 

 common dense tissue for the greater portion of their length ; 

 but this rises into points near the extremity, whose interspaces 

 are filled by a more delicate pellucid web, forming the trumpet- 

 mouth, which again is furnished with subconical points along 

 its edge. From the centre of this trumpet-mouth projects the 

 tentacle (e), in form of a short clavate column, with a basal 

 bulb, which under high magnification divides into oblique 

 leaves. The tentacle-tip usually reaches beyond the level of 

 the trumpet-mouth, to the extent of about half of the latter's 

 diameter ; but it can be retracted wholly out of sight, without 

 any sensible change of form in the sheath. The length of the 

 sheath alone is more than the greatest width of the body. 



Branchiaj three on each side, springing from a sort of pal- 

 lial ridge clothed with the loose membrane already alluded to. 

 They a])pear at first sight to be stout ovate j)rocesses with 

 short thick peduncles. But prolonged examination reveals 

 that each is a broad thick leaf ( /'), of nearly circular outlii)e, 

 whose edge is deeply incised, so as to form five pairs and a 



