Mr. Jeffreys on British Mollusca. 119 



distributionists. As, however, few of these shells were taken in a 

 living state, it may be said that some of them were fossil, or had 

 been carried by snbmarine currents to the spot. Now, although 

 no chemical or other test has yet been discovered for distinguishing 

 what are called fossil from recent shells, whose cavities or tissue 

 are not permeated by mineral matter, the general appearance of 

 all the specimens in question, and their hyaline texture, instead 

 of the dull aspect and opacity of fossil shells from even the 

 newest strata of the Tertiary system, sufficiently make out a 

 prima facie case of their recent origin; while it is highly impro- 

 bable that various currents would set in quite opposite directions 

 for many hundred leagues, and bring shells from the very bottom 

 of the sea to this particular locality. It is, on the contrary, as 

 I submit, a fair inference, that all the Mollusca whose remains 

 have been thus brought to light, lived and died within a few 

 miles of the place of their ultimate sepulture. How far their 

 continued submersion in the sea for many ages, beyond the 

 reach of atmospheric influence, may have prevented any change 

 in their composition, and given them a recent appearance, in- 

 stead of that of true fossils, is another question, which I am not 

 prepared to answer. 



[Since the above was written, I have received from Mr. Waller 

 a very interesting paper of his on the above subject, which has 

 just been published in the ' Transactions of the lioyal Dublin 

 Society,' and to which I beg to refer my readers for an exposi- 

 tion of his views. I may observe, that the fragments of a shell 

 which I at first supposed to belong to a Tarritella allied to 

 T. polaris, and which JMr. Waller has provisionally named 

 " Hibernicuj" I have since ascertained to be the Scalaria Esch- 

 richti of Holbcill and *S'. horealis of Beck. The results of this 

 dredging exploration are reserved for the next meeting of the 

 British xVssociation for the Advancement of Science, under whose 

 auspices it was partly conducted ; and I therefore abstain from 

 making any further allusion to it.] 



While mentioning shell-sand, it may not be amiss to remark 

 that it ought to be carefully passed through sieves of various 

 degrees of fineness before examining it ; for otherwise the eye 

 will be distracted by the unequal size of the objects submitted 

 to it, and some of the smaller shells may be concealed from view 

 by larger and coarser ones. If by chance this suggestion is 

 adopted by French couchologists, 1 hope they will not be led by 

 an accident of mistranslation into a similar error to that which 

 I noticed in a recent number of the ' Journal de Conciiyliologie,' 

 in which I was said to recommend using the drcdyc to get uj) 

 sea-weed from different depths of the sea, for the purpose of 

 collecting minute shells ! 



9* 



