168 Mr. J. G. Jefireys on the Marine Testacea 



ciation for the Advancement of Science^ on British Marine 

 Zoology^ as well as in his introduction to the ' British ]\Iollusca/ 

 he has enumerated certain species which he called " peculiarly 

 Northern " or " Boreal;" others which, according to his account, 

 show the more powerful influence of the Scandinavian element 

 in our fauna, and which he assigned to a "Celtic" type; some 

 which he designated as " peculiarly British," and again others 

 that he found to occur in our seas only in a few isolated patches 

 which he regarded as " Glacial " outliers. Now, of the first- 

 mentioned or " Boreal " species, I found several in the INIedi- 

 terranean (viz. Chiton Hanleyi, Mangelia brachystomn , and Necera 

 costellata), another {Mangelia Leufroyi or Boothii) has been 

 described and figured by Philippi as a recent Sicilian species, 

 and a fifth {Scissu7-eUa crispata) 1 believe to be identical with the 

 Scissurella decussata of D'Orbiguy. Of the second division or 

 " Celtic " species, I met with Tapes pullastra (of which the Venus 

 geographica of continental authors is a variety), Acmcea virginea, 

 Lucina barealis or radula, and Lucina flexuosa ; and Philippi 

 has given Trochus millegranus and Eulimella Macandrei (his 

 Melania Scilla) as Sicilian species. Of the third division, or 

 " peculiarly British " species, several (as Jeffreysia diaphana, 

 and the so-called Skeaece, besides Ai^giope cistellula of Searles 

 Wood, which I think cannot be distinguished from the Orthis 

 Neapolitana of Scacchi) also occurred to me in the Mediterra- 

 nean ; and of the last division or " Glacial " species I detected 

 three species (namely Xucula decussata, Necera cuspidata, and 

 Cardium Suecicum or minimum), and Philippi has given another 

 [Area raridentata or Peduncuhides) as Sicilian. I have more- 

 over good reason to believe, judging from the very small extent 

 of ground which has been as yet examined, that these exceptional 

 species may be considerably added to when the wide extent of 

 the Mediterranean Sea and its coasts has been more explored. I 

 have myself been enabled to add to the Mediterranean fauna, in 

 the short space of time which I devoted to this research, more 

 than thirty species which had been hitherto considered as 

 restricted to the British seas. It is obvious that negative evi- 

 dence of the occurrence of any species (and especially of those 

 which inhabit deep water) in any given area of sea is inadmis- 

 sible ; and naturalists do not differ from logicians or lawyers in 

 rejecting such evidence. 



It may indeed be argued in favour of the division into special 

 or limited areas, that the species I have named, have, in the 

 course of time, migrated or been diffused from the birthplace of 

 their primseval ancestors, or from what is now called the centre 

 or focus of their creation, and that this migration or diffusion 

 has been facilitated by causes now in operation, and especially 



