I 



. Mr Gray on Testaceous Mollusca. 9S 



hood of Tilbury Fort, which gradually become more or less 

 fresh in proportion to the quantity of rain that falls between the 

 periods of opening the sluices. It is to be observed that the 

 specimens found in this situation are rather thinner and more 

 produced posteriorly than those usually found in the sea. The 

 species in question is also, according to Niisson, found in the 

 brackish water on the shores of the Baltic, but I am not aware 

 whether or not it is there subject to a similar variation in form. 

 Niisson observes, however, that the marine species found in those 

 localities are generally smaller than those found in other situations. 

 From this list of exceptions to the general rules which have 

 commonly been regarded as decisive of the localities inhabited by 

 recent shells, and of the nature of the deposits in which the fossil 

 species are found, it is manifest that those rules cannot safely be 

 made use of for practical purposes without considerable reserva- 

 tion. 



On some Circumstances connected with the Original Suggestion 

 of the Modern Arctic Expeditions, Communicated by the 

 Rev. W. ScoRESBY, B. D., in a letter to the Editor of the 

 Edinburgh New Philosophical Journal. 



Statements having recently appeared in the " Literary 

 Gazette," in an abstract of a paper by Captain Beechey, read be- 

 fore the Geographical Society; and in the Quarterly Review, in 

 an article on Sir John Ross's account of his late voyage of dis- 

 covery, &c. at variance with, or in contradiction of, the account 

 given by Sir John Ross of my connection with the origination 

 of the Modern Arctic Expeditions, — I consider it but justice 

 to that gentleman, as well as to myself, to put the public in pos- 

 session of the actual facts respecting the nature and measure 

 of the participation which I really had in the revival of the cele- 

 brated question, out of which these curious expeditions appeared 

 to spring. 



The statement in die Quarterly Review, to which I refer, oc- 

 curs in the introductory passage of the first article of No. CVII., 

 wherein (explanatory of the reasons for undertaking the review 

 of Sir John Ross's publication) it is stated : — 



