F. W. Harmer — The Coralline Crag Jfolluscan Fauna. 29 



subsequent to the coming into existence of the present fauna there 

 was more open connection between the latter and the Mediterranean 

 than there is at present. The distinctively Southern character of the 

 fauna of the Coralline Crag is further shown by the comparatively 

 large proportion of its shells that do not now live so far to the 

 north as the seas of Great Britain, but this also comes out more 

 strongly when we confine our attention to its more abundant forms. 

 While, as has been shown, there is only one among the 132 recent 

 European Mollusca, representative of the formation, which is British 

 and not Southern, there are 80, or 26 per cent., which are Southern 

 and not British. But among the forms usually regarded as British, 

 there are nine — viz. : Cerithium Metaxa, Caecum trachea, ModioJa 

 rhombea, Limopsis aurita, Scaccliia orbicularis, Woodia digitaria, 

 Donax politus, Tltracia pubescens, and Poromya granulata, charac- 

 teristic shells both of the Mediterranean and of the Coralline Crag 

 — which are either confined to the south-western portion of our seas, 

 or have been included in lists of the British fauna because of the 

 occasional discovery of some rare specimens on our coasts. If we 

 regard these nine species as Southern, we have 44 out of 132, or 

 more than one-third, which are Southern and not British. In a 

 word, the abundant shells of the Coralline Crag which are now living 

 in European waters are practically all Southern forms, though some 

 of them range also into Northern seas, but the few shells which are 

 exclusively boreal are, with the one exception named, exceedingly 

 rare. It may safely be said that if it were possible to count shells 

 instead of species, we should meet with some thousands of specimens 

 of recent Southern Mollusca in the Coralline Crag for every recent 

 boreal shell we could discover. We find also among the extinct 

 species, abundant in the Coralline Crag, a greatly preponderating 

 number of genera of a decidedly Southern character. Among these 

 may be mentioned, Voluta, Terebra, Cassidaria, Pyramidella, Nuci- 

 nella, Scintilla, Erycinella, Panopaa, and Pholadomya, the last of 

 which is tropical, as is also the West Indian shell, Erato Maugeria, 

 and both these are abundant. 



On the other hand, no shell, in Mr. Wood's opinion, of an ex- 

 clusively Arctic character has been discovered in the Coralline 

 Crag, except a single valve, which he referred with a good deal 

 of doubt to the species Ceritluopsis lactea ; but among the extinct 

 forms there is one, Glycimeris angusta, which is not uncommon, 

 which belongs to a Northern genus. 1 Attention has been called to 

 the profusion of the different species of Astarte, as giving a boreal 



1 Professor Prestwick gives a list of about a dozen species of Mollusca ■which he 

 claims as Northern (Q.J.G.S., vol. xxvii, 1871, p. 135). Five of these, however, 

 range to the south as well as to the north of our shores ; and as to the rest, with the 

 exception of the one already named (Bitcciuopsis Dalei), and another, Trichotropls 

 borealis, -which is very rare in the Coralline Crag, he follows Dr. Gwyn Jetfreys 

 in considering shells regarded as extinct bv Searles "Wood and others as varieties 

 merely of existing species. For example, he believes Astarte Onialii to be the 

 equivalent of A. toalata, an American shell, and TeUina obiiqua that of T. lata, 

 an entirely distinct form. Mr. Wood had the opportunity of weighing Dr. Jeffreys' 

 views, aud he has given in the Supplement to his Monograph his reasons for 

 differing from them. I agree with Mr. Clement Eeid and others in following 

 Mr. Wood's opinion as to this. 



