CELTIC PROVINCE. 



361 



The wide expanse of the Baltic affords no shell-fish unknown to the coasts 

 of Britain and Sweden. The water is brackish, becoming less salt northward, 

 till only estuary shells are met with, and the Litorinse and Limnsans are 

 found living together, as in many of our own marshes. This scanty list is 

 taken from the ]\Iemoirs of Dr. Middendorff and M. Boll. 



Buccinum undatum. 

 Purpura lapillus. 

 Nassa reticulata. 

 Litorina litovea. 

 Patella (taveutina). 

 Hydro bia muriatica. 



Neritina fluviatilis. 

 Limujea auricularia. 



,, ovata. 

 Mytilus edulis. 

 Donax (trunculus). 

 Cardium edule var. 



Tellina Balthlca. 



„ tenuis. 

 Scrobicularia piperata. 

 Mya arenaria. 

 „ truncata. 



IV. LusiTANiAN Province. 



The shores of the Bay of Biscay, Portugal, the Mediterranean, and 

 N. W. Africa, as far as Cape Juby, form one important province, extending 

 westward in the Atlantic as far as the Gulf weed bank, so as to include 

 Madeira, the Azores, and Canary Islands.* 



In the Atlantic portion of the province occur the following genera, not 

 met with in the Celtic and Boreal seas, although two of them, 3Iitra and 

 Mesalia, occur ou the coast of Greenland. 



* In the nortliern part of the Lusitanian province are the Pilchard fisheries; in 

 the Mediterranean, the Tunny, Coral, and Sponge fisheries. 



The Gulf-weed banks (represented in the map) extend from 19° to 47° in the 

 middle of the North Atlantic, covering a space almost seven times greater than the 

 area of France. Columbus, who first met with the sargasso about one hundred 

 miles west of the Azores, was apprehensive that his ships would run upon a shoal. 

 (Humboldt.) The banks are supposed by Prof. E. Forbes to indicate an ancient coast- 

 line of the Lusitanian land-province, on which the weed originated. Dr. Harvey 

 states that species of Sargassum abound along the shores of tropical countries, but 

 none exactly correspond with the Gulf-weed (5. bacciferum). It never produces 

 fructification — the "berries" being air-vesicles, not fruit — but yet continues to grow 

 and flourish in its pres^^nt situation, being propagated by breakage. It may be an 

 abnormal condition of 5. vulgare, similar to the varieties of Fucusnodosus (Mackayi) 

 and F. vesiculosus which often occur in immense strata ; the one on muddy sea-shores, 

 the other in salt marshes, in which situations they have never been found in fructi- 

 fication. {Manual of British Algce, Intr. 16,17.) 



