178 



MEDITERRANEAN PROVINCE. 



extension of species, southern forms find a more 

 congenial one on the Algerine coast than elsewhere. 

 If to this condition is superadded that of the inflow 

 from the Atlantic, setting along the North African 

 coast, there exist good reasons for expecting certain 

 local peculiarities. 



The Atlantic inflow determines that marked 

 preponderance of pelagic animals which is to be 

 noticed about the Gut of Gibraltar. The forms of 

 Mollusks which are western are such as Ervilliacas- 

 tanea, Siphonaria concinna, Acmcea virginea, Mesalia 

 sulcata and M. striata, Cymba olla, Lutraria ellip- 

 tica, Venus striatula, Astarte sulcata and A. triangu- 

 laris, Natica intricata ; these are all Lusitanian 

 and "West African species. In addition, these 

 forms and some others are not found fossil in any 

 of the raised sea-beds of the older Mediterranean, 

 and may therefore be looked upon as species which 

 as yet have made only a limited progress in colo- 

 nizing this internal sea. 



The Eastern Mediterranean is inseparably con- 

 nected with Edw. Forbes' researches into the distri- 

 bution of animal and vegetable life in depth ; he 

 found, proceeding from the highest upward limit 

 of these waters downwards, that there were the 

 following distinct zones. 



The Littoral Zone has a depth of only two fathoms ; 

 and, small as this is, it yet admits of a twofold di- 

 vision, even in this nearly tideless sea. The narrow 

 interval between tides is thus described by Ed. 



