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periods, and, to show the progress of discovery and rectifica- 

 tion, I now present them pretty much in their original form. 

 The first account was written during the summer months of 

 1849, after an examination of many hundreds, I may say, of 

 nearly all the varieties of Littorina rudis, which have long 

 occupied a position as species, to which it will appear they are 

 not entitled. 



In close connection with this subject is a very short corre- 

 spondence between Professor Forbes and myself. I have no 

 copies of my letters, for it has always been an irksome task 

 to me to copy what I write ; I trust to memory ; and if I 

 have misstated any point, I humbly submit to correction. As 

 Professor Forbes's letter is strictly malacological, I feel con- 

 fident, from his well-known liberality, that he will not con- 

 sider an apology necessary for the insertion of the following 

 extract : 



" West Lulworth, near Wareham, Dorset, Nov. 1849. 



" I should like to know what opinion you have come to 

 respecting the specific value of the forms of the Littorinae 

 you enumerate. For my part I can only recognize Litto- 

 rina littorea, L. petrtea, L. neritoides and L. rudis. I am in 

 doubt, however, whether L. jugosa should not also be held 

 distinct." 



Being in a position to answer decisively, I wrote to the 

 effect, that having carefully examined nearly all the animals 

 of the varieties termed by authors L. tenebrosa, L.juyosa, 

 L. zonaria, L. rudissima, L. fabalis, L. neglecta, &c., I found 

 them to be identical with each other, and mere varieties of 

 L. rudis, and consequently that that portion of the genus 

 Littorina consisted, agreeably to his views, of only L. littorea 

 and L. rudis ; I however added, that I believed the Lacuna, 

 not excepting L. crassior, were confined to one or two species. 



As the genus Littorina has long been the depot of many of 

 its varieties, improperly promoted to species, it occurred to me 

 that a good opportunity offered itself for making a few re- 

 marks, with the view of checking, if possible, this inconvenient 

 practice, by pointing out the great detriment that resulted to 

 science from the fabrication of species on insufficient grounds. 



