Mr. ft. M f Andrew on the Comparative Size of Molluscd. 



14. Littorina rudis. I do not question the correctness of Mf. 

 Jeffreys' s remarks, but do not see that they in any way affect 

 my statement. 



15. Scalaria communis. Notwithstanding that Mr. Jeffreys 

 has not seen large Mediterranean specimens, it is nevertheless a 

 fact that they attain a greater size in Gibraltar than in England. 

 The largest of my Gibraltar specimens exceeds in size the largest 

 of my English, and the average of my Gibraltar the average of 

 my English specimens. 



16. Bulla hydatis. I refer to the shell so called by Forbes 

 and Hanley (whether correctly or incorrectly named is not to 

 the purpose), which is both abundant and large at Vigo Bay. 



17. Murex erinaceus. I may have given small specimens to 

 the British Museum. I repeat that the species attains larger 

 dimensions upon the coasts of Spain than on those of Britain, 

 both as regards extreme and average magnitude. 



18. Cerithium reticulatum. I will not enter upon the ques- 

 tion of varieties. I wish, however, to amend my remark upon 

 this species, and to substitute that the Spanish specimens are 

 fully equal in size to the British, and larger than those of North 

 Drontheim. 



19. Triforis perversa. I do not see how Mr. Jeffreys' s remark 

 upon the last species applies to this. I repeat that the speci- 

 mens of it attain much greater size in the Mediterranean than 

 on the British coasts. 



20. Aclis supranitida. I acknowledge that I was mistaken in 

 my remark regarding this species. Upon comparing my only 

 Madeiran specimen with British, I find it to be about equal, but 

 not superior, in size. 



Mr. Jeffreys' s information respecting Tellina balaustina is only 

 important with reference to the distribution of the species. The 

 result of my observation is limited to the fact that specimens 

 diminish in size but increase in frequency from the Atlantic 

 eastward in the Mediterranean. 



Of Teredo, I am unacquainted with the species. Montagu, 

 who probably confounded more than one species under the 

 name of Teredo navalis, speaking of it, says, " This part (the 

 tube) is rarely above three-quarters of an inch in diameter at the 

 larger end, and a foot in length in our climate, but exceeds that 

 in the more southern parts, from whence it was brought into 

 our harbours, to the great destruction of our ships as Linnseus 

 justly observes, calamitas navium" It is certain that ships are 

 much more exposed to the ravages of these animals when in 

 southern latitudes; and it is evident that before the custom 

 prevailed of protecting the bottoms of ships with copper, the 

 transportation of species from their original habitat to the re- 

 motest regions was inevitable. 



