Mr. J. G. Jefrreys on British MoUusca. 41 



Some of the species now noticed are " very rare," as far as 

 specimens have been liitlnrto discovered; but it must be borne 

 in mind that a few baskets of shell-stuff, or liandfuls of sand, 

 obtained l^y dredginjj, are but a very insi<rniticant sample of 

 those vast and various patches of sea-bottom which are dispersed 

 over so many thousands of square miles within the line of sound- 

 ingcs on our coasts. Further discoveries, therefore, both of species 

 and specimens, may be confidently expected. 



It is true that all the species which I here propose to describe 

 or notice as new to this country, arc small, and most of them 

 even minute; but, far from ado])ting the maxim "dc minimis 

 uon curat Lex," science regards with as much interest the tiniest 

 productions of nature as the mammoth or the leviathan of the 

 deep ; and the revelations of the microscope are not less wonderful 

 and important than those far-distant worlds which the telescope 

 discloses to mortal eyes. 



The recent sej)aration by M. Milne-Edwards (and which has 

 been adopted by M. de Quatrefages and other eminent zoolo- 

 gists) of the Tunicata from the true Mollusca has further nar- 

 rowed the limits of this large and heterogeneous division of the 

 Invertebrata, and might almost tempt Naturalists to revert to the 

 use of the term (Vermes) Testacea, which the great sj'stematist 

 Linmcus proposed for the reception of what arc now considered 

 as Mollusca proper. 



" Multa renascentnr, qure jam oeciilere, cadentque 

 QiL-u nunc sunt in lionore vocabula, si volet usus, 

 Quein peues arbitrium est, ct jus et norma loquendi." 



All the jMollusca, as at present defined, are more or less in- 

 vested by, or secrete, shells ; although the latter are occasionally 

 in a rudimentary or imperfectly developed state, or are only 

 found during the earliest period of their growth, as is the case 

 with the Cephalopoda, Limacidse, and Xudibranchiata. There are 

 unquestionably some exceptions to this proposition, especially 

 in some of the Cuttles and Slugs; but an exception proves the 

 rule, and it cannot be said with less justice, that the true Mol- 

 lusca are not testaceous, than that certain species of Odostomia 

 which are destitute of teeth therefore do not belong to that 

 genus. Similar instances in other branches of natui'al history 

 will doubtless occur to many of your readers. 



The discovery on the east coast of Zetland of Rissoa glabrata, 

 which has been hitherto regarded as exclusively Mediterranean 

 (to which must be added, among the Foraminifera, Peneroplis 

 planatus), and also, in the same locality, of Area nodulosa, 

 an Arctic species, as well as, in the north of Ireland, of 

 Mangelia Holbollii, an inhabitant of the North Seas, makes 



