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ranean, viz., cytheria cliione and venns verrucosa, reach their 

 highest latitude on the coast of Carnarvonshire. Several other 

 well-known inhabitants of the Mediterranean extend only 

 along the western shores of the British isles ; being found in 

 the neighbourhood of Cornwall and Scilly; again, in the 

 south of Ireland, and round the west coast of that country 

 to the Hebrides and even Zetland. This is the case with 

 solenecurtus candidus, psammobia costvdata, lucina spinifera, 

 cytheria minuta, pecten similis, natica sordida, pleurotoma 

 teres, and erato levis. TeUina balaustina and area raridentata 

 have only been met with in the west of Ireland and the Isle 

 of Skye. It is worthy of remark that these are mostly old 

 species, all but two being recorded as fossil in the tertiary 

 beds of Sicily, and that they are not found in either the British 

 or St. George's Channels ; whether this circumstance is to be 

 regarded as corroborating the opinion that these channels 

 have been formed by the sea at a recent geological period, I 

 would merely suggest for consideration. Two species of 

 necera, N. costellata and N. abbreviata, inhabiting both the 

 Mediterranean and coasts of Norway, are only known in one 

 British locality, viz., Loch Pyne, where they were discovered 

 by Professor Forbes and myself in 1845. Of pecten pes felis, 

 recorded from the Egsean, a single individual, dredged by my- 

 self in Loch Fyne, is the only specimen that has been procured 

 alive on our coasts 



" I will now proceed to those marine occupants of the arctic 

 or northern division of the ocean, which apparently reach the 

 southern limit of their range at different points within the 

 area of the British seas. Of these, some only extend to the 

 neighbourhood of Zetland and Orkney ; as for example astarte 

 borealis, of which I obtained a recent valve off Zetland, and 

 have seen perfect specimens from Spitzbergen ; of margarita 

 undata, otherwise only known as a Greenland species, I pro- 

 cured a live specimen near Lerwick. Also trochus formosus, 

 fusus albus, cerithuim nititidum, with a rostellaria and two 



