4302 Mollusks. 



In the Introduction to ' The History of the British Mollusca,' it is 

 said that four, perhaps six separate districts must be visited before a 

 conchologist could personally collect a complete set of British shells; 

 viz., the Channel Islands, the South-West coasts of England, the 

 West coasts of Scotland, the Zetland Islands, the northern half of 

 the German Ocean, and the West coasts of Ireland. The Moray 

 Firth, or that triangular inlet or arm of the German Ocean, which has 

 Peterhead, Inverness, and Duncansbay Head at its angles (Zool. 

 3455), of course must be assigned to the fifth of these districts. 

 However, it will be seen from the following enumeration that it con- 

 tains many species whose chief British habitat is the fourth or Zetland 

 area : this may be accounted for by the strong tidal current that sets 

 into it from the North through the Pentland Firth. Messrs. Forbes 

 and Hanley also state in the Introduction (p. xvii.) that " our marine 

 molluscan Fauna, when considered with respect to its home arrange- 

 ments, may be said to be composed of examples of no fewer than nine 

 types," viz., the Lusitanian, the South British, the European, the 

 Celtic, the peculiarly British, the Atlantic, the Oceanic, the Boreal, 

 and the Arctic. Although the following list comprehends all but one 

 (Syndosmya alba) of the forty-three species given as characteristic 

 members of the European, and all but four (Lacuna puteolus, Man- 

 gelia turricola, Thracia distorta, and Trophon muricatus) of the forty- 

 six species characteristic of the Celtic type, yet the northern locality 

 and already ascertained molluscan products would, it is presumed, fix 

 the Moray Firth as one of those places that chiefly yield examples of 

 the Boreal or eighth type, thus described: — st VIII. We have before 

 remarked that in the northern division of the British seas there are 

 many species either not found more to the South, or else becoming 

 rarer as we proceed southwards. Some of them, too, are only to be 

 met with in peculiar and limited localities, grouped together like iso- 

 lated colonists. The majority of these northern forms belong to au 

 assemblage that constitutes the Bokeal type of our molluscan Fauna. 

 They are all species that thrive best in seas to the North of Britain, 

 and many of them range across the Boreal Atlantic, or, at least, are 

 found on both sides, but only within cold waters. They are not, how- 

 ever, to be considered as strictly Arctic. To this group we may as- 

 sign such examples as Acmaea testudinalis, Astarte compressa and 

 elliptica, Cardium Suecicum, Cerithium metula, Chemnitzia fulvo- 

 cincta ? Chiton Hanleyi and marmoreus, Crania anomala, Crenella 

 nigra, Cyprina Islandica, Emarginula crassa, Fusus Norvegicus and 

 propinquus, Hypothyris psittacea, Leda caudata and pygmaea, 



