Mr. Thompson on the Mollusca of Ireland. 89 



gnosis of T, arbor escens in Fleming's Brit. Anim. p. 284, — 

 " branchiae 6 on each side, in the form of plumose tubercles/' 

 applies equally to the T. lactea, as does the detailed descrip- 

 tion in the following particulars — "foot narrow, sides com- 

 pressed; cloak smooth, its margin above the mouth with 4 

 plumose appendages ; branchiae decreasing in size towards 

 the tail," — this in T, lactea is very small. On comparing 

 it with a specimen of T. arbor escens from St. Andrews, in Mr. 

 E. Forbes's collection, the most striking diiFerence is in the 

 shorter body of T, lactea, and consequently the nearer ap- 

 proximation of the branchial filaments, which are considerably 

 larger than in its congener, whilst the sheaths of the tenta- 

 cula are somewhat less developed than in that species: the 

 colour too is very different, T, arbor escens being of a rose-red, 

 varied with darker spots and markings. 



The specimen occurred to me when dredging at the en- 

 trance of Strangford lough, in the month of October, in com- 

 pany with Mr. Hyndman. 



Eolidia papillosa, Johnst. Mag. Nat. Hist. 8. 376. fig. 35. 

 Annals N. H. 1. 118. 



Of this fine species, three individuals were found by Dr. 

 Lloyd (of Malahide) and myself, under stones at Lambay is- 

 land, on the 1st of June; at the same time their spawn, just 

 as described and figured by Dr. Johnston in Mag. N. H. as 

 above-cited, was obtained. One of these animals examined 

 critically had 25 lateral rows of branchial processes, and about 

 12 of these to each row. 



Eolidia Cuvierii, Johnst. Ann. Nat. Hist. 1. 120. pi. 3. 

 fig. 9—11. 



Among the Nudibranchia which I owe to the kindness of 

 Mr. Allman, was a small individual of this species, taken by 

 him at Courtmasherry harbour, in the autumn of 1838. 



Eolidia rufibranchialis, Johnst. Mag. Nat. Hist. 5. 428. 

 fig. 85. Annals N. H. 1. 121. 



The first specimen of this Eolidia that I am aware of being 

 taken on the Irish coast, occurred to myself at Newcastle, 

 county Down, in August, 1836, but besides its careful pre- 



Ann. Nat. Hist. Vol. 5. No. 29. April 1840. h 



