348 Mr. H. E. Strickland on Thalassidroma melitensis. 



naturalist himself, who moreover has given no other detail re- 

 specting its internal organization than the short description of 

 the generative apparatus which I have already noticed. It is 

 then a genus concerning which nothing can be determined. The 

 genus Placobranchus, established by Van Hasselt, has been re- 

 ferred to this order solely from the analogy which it presents 

 with the genus Acteon. The last two genera, Pelta and Cha- 

 lidis, then remain, on the subject of which it is impossible for me 

 to oppose my observations to those of M. de Quatrefages*. If 

 however we consider the numerous errors of observation which 

 I have pointed out in the investigations of that naturalist, and 

 the proofs of which it will be easy for me to furnish, — if moreover 

 we admit that these errors may have been more easy to commit 

 on animals which are almost microscopical, it will follow, I think, 

 that the facts which M. de Quatrefages has enumerated in the 

 organization of these mollusca do not present a degree of certainty 

 sufficient to be accepted in sound zoology, — these facts being in 

 contradiction to all other received facts and to all analogy. 



In replying to the assertions of M. de Quatrefages in this short 

 notice, I have had occasion sometimes to argue upon facts which 

 do not appear to me to have received the most rational explana- 

 tion, and every one may consequently appreciate the value and 

 justness of my arguments ; but most frequently I have found that 

 I disagreed with the facts themselves, and have then been obliged 

 to question their accuracy. I am aware that it remains for me 

 to oppose facts to them ; but these proofs, which I have in my 

 possession, I shall submit together with my work to the Academy, 

 and they will, I hope, place beyond a doubt all that I have ad- 

 vanced and all that I have objected to. 



XLV. — On Thalassidroma melitensis, Schembri, a supposed new 

 species of Stormy Petrel. By H. E. Strickland, M.A. 



In the valuable paper on the birds of the Ionian Islands by Capt. 

 H. M. Drummond (Annals of Nat. Hist. vol. xii. p. 422), that 

 gentleman remarks that the bird which he had considered to be 

 Thalassidroma pelagica was more probably the T. melitensis, a new 

 species discovered at Malta by Sig r . Schembri, and supposed to 

 be peculiar to the Mediterranean. In the excellent little work 

 of the last-named author, entitled 'Catalogo Ornitologico del 

 Gruppo di Malta/ published in 1843, is a description and figure 

 of the Thalassidroma melitensis, the distinctive characters of which 



* I have not been able to examine the objects collected and described by 

 M. de Quatrefages, that naturalist not having deposited them in the galleries 

 of the Museum. 



