vi A MONOGRAPH OF THE 



" Body ovate, mottled brown and white ; along each side an obsolete row of tubercles, 

 somewhat dilatable, extending from the tentacula to the vent : tentacula four, long, both pairs 

 originating from the upper part, and approximating ; the anterior shortest, setiform, inclining 

 forwards ; the other filiform, reflecting backwards, the same colour as the body : vent 

 situated near the extremity of the back, surrounded with eight or nine branched appendages. 

 Length three eighths of an inch. Rare." 



Montagu, whose short description we have inserted entire, is the only person who has 

 met with this obscure species, which requires further illustration. 



16) Tritonia alba. 



We have occasionally obtained this new species at Cullercoats, in company with T. plebeia, 

 on masses of Alcyonium digitatum, brought in on the fishermen's lines. In its characters it 

 approaches so nearly to T. Hombergii that we were for some time inclined to consider it the 

 young of that species ; but as the individuals were always of small size, and no intermediate 

 examples were found connecting it with the adult T. Hombergii, which is very rarely brought 

 in on the fishing lines, and as the specimens found were constantly of a white colour, some 

 doubt might be considered to rest upon their supposed identity. The point has been satis- 

 factorily settled by an examination of the tongues of the two species. That of T. Hombergii 

 is very broad, and has the lateral spines all simple ; the tongue of T. alba is narrower, and 

 has the spines, which are rather more slender than in the other species, branched or denticu- 

 lated on the outer margin. This difference could not be the result of age. But to satisfy 

 ourselves more fully upon this point, we have examined the tongue of the undoubted young of 

 T. Hombergii of the same size as T. alba, got along with the adult in Torbay, and find that the 

 spines have the same simple character as in the large specimens. There can be no doubt, 

 therefore, of their distinctness. We have not had an opportunity of comparing them 

 together, so as satisfactorily to define the points of difference in their external characters, 

 but speaking from recollection, we should say that the new species is rather flatter and less 

 tuberculated, the pallial ridge is more produced, the branchiae shorter and less perfectly lami- 

 nated, and that the veil has fewer digitations than in T. Hombergii of the same size. The 

 whole animal is also more delicate and transparent. 



(17) ScYLLiEA PELAGICA. 



Scyllaa pelagica, Linn., Syst. Nat., 12th ed., v. l,p. 1094. 



Cuv., Ann. du Mus., v. 6, p. 416, pi. 61, figs. 1—7. 

 For. and Hani., Brit. Moll., v. 3, p. 584, pi. aaa, fig. 5. 



We are unfortunately unable to add anything to the short description of this species 

 given in our Synopsis. A single specimen was sent to us in spirits by Mr. W. P. Cocks, of 

 Falmouth, in April, 1847, being one of three which he found alive among a large mass of sea- 

 weed thrown up after a storm. They were attached to the frond of a weather-beaten 

 Laminaria bulbosa, from deep water, thrown upon the rocks near Pendennis Castle. Mr. 

 Cocks remarks that their appearance when alive was gelatinous, transparent, and of a light 

 cream-colour without markings. He kept them for three days in sea-water, but being unwell 



