334 LITTORINID#. 
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 followmg 
extract :— 
“* West Lulworth, near Wareham, Dorset, Noy. 1849. 
“JT should like to know what opmion you have come to 
respecting the specific value of the forms of the Littorine 
you enumerate. For my part I can only recognize Litto- 
rina littorea, L. petrea, L. neritoides and L. rudis. I am in 
doubt, however, whether L. jugosa should not also be held 
distinct.” 
Being im 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. jugosa, 
L. zonaria, L. rudissima, L. fabalis, L. neglecta, &c., 1 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 Lacune, 
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 poimting out the great detriment that resulted to 
science from the fabrication of species on insufficient grounds. 
