Marine Zoology. 71 



statement was that such species were universally diffused through 

 our seas. The researches embodied in this Report, however, put 

 beyond question the fact that there arc marked peculiarities in the 

 distribution of British marine animals, and that though there are 

 numerous species common to the whole area, there are also numerous 

 species peculiar to parts of that area. We have clear evidence of 

 more elements than one contributing to the composition of our sub- 

 marine population, of a souAern element, derived from the Lusi- 

 tanian provinces of the European seas, of a northern element 

 introduced from the Scandinavian seas, of a Celtic element having 

 its centre within our own region, of an oceanic element manifested 

 by the floating Gasteropoda and the Pteropoda that reach our shores, 

 and of an arctic element due to causes which were in action before 

 the British Isles had assumed their present conformation.* The 

 following statements, founded mainly on the data contained in the 

 tables, will serve to illustrate the phestiomena, as far as this Report 

 is concerned. 



The northern and southern frovinces of the western coast of 

 Great Britain may he distinguished hy certain Mollusca of the 

 Littoral Zone^ enumerated in the Report. 



The differences between the northern and southern provinces are 

 equally shewn hy the suh-littoral testacea, as shewn in the Report. 



Numerical comparisons of the Testacea and hard Echinoder- 

 mata inhabiting the regions explored, with the total number of 

 British species. — In the Report, one of the striking features is the 

 small number of testacea and hard echinoderms inhabiting the 

 British Seas, which do not live upon the western shores of Great 

 Britain ; such as are beyond their limits, are either of excessively 

 southern and scarcely British character, as Haliotis tuberculata, 

 Jeffrey sia opalina, Rissoa lactea, and Murex corallinus ; or oceanic 

 forms of lanthina, Hyalcea, and Spirialis ; or species probably of 

 arctic origin, extending only to our north-eastern coasts, as Fusus 

 norvegicus and Turtoni, Natica, Kingii, Hypothyris psittacea, and 

 Goniaster equestris. The number of doubtful or not sufficiently 

 investigated forms is also very small. A considerable number of 

 genera have no, or few, representative members in the Scottish and 

 Enghsh columns of western sub-littoral species ; these are either 

 extra-limital, as Hyalcea, Haliotis, and Hypothyris ; or excessively 

 rare in our seas, as Avicula^ Stylifer, Cidaris, and Astrophyton ; 

 or oceanic, as lanthina and Spirialis ; or wholly or mainly littoral, as 

 Littori7ia,Otina, Conovulus, Truncatella, Jeffrey sia, iSArewea (proper), 

 Patella, PleurobranchuSy Teredo^ Xylophaga, Petricola, Vene- 

 rupis, Ceratisolcn, Turtonia, Galcomma, MytiluSy Asterina, In 



♦ See the Memoir on the British Fauna and Flora, in the first volume of the 

 Memoirs of the Geological Survey. 



