rZ DESCRIPTION OF PLEUROBRANCHUS. 



round points, beneatli the skin, at the outer and upper 

 part of the base of dorsal tentacles. 



General colour golden or orange chrome ; the veil 

 and foot rather paler; under side of the foot (fig. 2.) 

 approaching to flesh-colour; showing a large black 

 cloud in the centre. The same spot seen dorsally 

 (fig. 1.) makes a cloud of brown, slightly tinged with red 

 in front. In this part, over the internal dark body, are 

 many dots which appear pellucid, and two or three 

 larger than the rest, through which the dark body 

 appears ; the yellow mantle between the dots assumes 

 a reticular appearance. The tentacles, especially 

 the dorsal pair, have a central line of dark brown ; 

 all are tubular, by the bending together of their sides, 

 but open in front and beneath, where the edges do 

 not quite meet. The branchial plume projects from 

 between the mantle and foot in crawling ; it is trans- 

 parent, and appears when viewed from above, to be 

 composed of many triangular laminae set imbricate, 

 and pointing backwards. Each lamina shows trans- 

 verse wrinkles. (See fig. 3.) Viewed laterally it is 

 seen to consist of a central stem, with about 18 pinna? 

 on each side, each pinna being again pinnated on 

 each side (fig. 5.) The stem, pinnae and pinnulse are all 

 dilated, inwardly, so that the stem, which is narrow 

 and slender at (5), is wide at (3), and the pinnoe are 

 the triangular laminae, whose wrinkles are in fact the 

 pinnulae. The organ is connected with the bottom of the 

 lateral sulcus for about two -thirds of its length by a sort 

 of membrane. The plume can scarcely be recognized 

 in its two aspects, even though examined again and 

 again in qjiick succession. It appears very sensitive 



