369 



is furnished with two massive lateral jaws bearing sharp prominent 

 dental processes on the anterior border, and with a pair of simple 

 tentacula having a dark ocellus at the outer side of the base of each. 

 A well-formed foot arises by a narrow pedicle from the under surface 

 of the body, immediately behind the ciliated collar. The creeping 

 disc is elongated in form, subquadrate in front, and tapers off gradu- 

 ally towards the posterior extremity. The latter part, correspond- 

 ing to the operculigerous lobe of other species, is speckled with 

 little clusters of dark pigment-cells, disposed so much after the 

 manner of those of the ciliated arms as to lead to the impression that 

 it ia one of the same series, or whorl of organs, to use botanical 

 phraseology. A pectinate gill extends beneath the mantle, along 

 the anterior third of the dorsal region, lying, as in most cases, in 

 advance of the heart. The visceral mass of the body, though elon- 

 gated, is but slightly curved upon itself, not exceeding half a turn. 

 The lobules of the liver, distended with large amber- coloured oil- 

 globules, may be distinctly seen through the transparent outer enve- 

 lope and shell. Single spherical otolithes are contained in the 

 acoustic sacs, and the lingual ribbon is lengthy and flexuous, pre- 

 senting a row of uncini on each side, with a series of minute 

 denticulations, pointing backwards on their anterior and posterior 

 borders. The uncini of opposite sides interlock with one another 

 so closely as to conceal the rudimentary segments of the rachis 

 almost completely. The shell is cartilaginous, transparent, planor- 

 bicular, and perfectly symmetrical, presenting four rows of minute 

 conical tuberculations on its convex or dorsal surface. The gyri of 

 the involute nucleus are so curved as to leave a central perforation ; 

 the mouth of the tube encroaches considerably on the last whorl, 

 and the outer lip is deeply notched between the two lateral rows of 

 tubercles. The author has named the species Jasonilla M c Leayiana. 

 The paper is accompanied with illustrative figures. 



V. Note " On the position of Aluminum in the Voltaic series." 

 By CHARLES WHEATSTONE, Esq., F.R.S. Received April 

 25, 1855. 



Having, through the kindness of Dr. Hofmann, been permitted to 

 examine a specimen of aluminum prepared by M. Claire- Deville, I 



