INTRODUCTION. XIX 



cite Acmcda virginea, Astarte sulcata, Buccinum undatum, 

 Chiton cinereus and ruber, Crenella decussata and discors, 

 Fusus antiquus and Islandicus ; the various species of 

 Lacuna, Liitorina littoralis, littorea and rudis, Lucina 

 horealis, Mactra elliptica and solida, Mangelia turricula, 

 Modiola modiolus, Mya arenaria and truncata, Mytiliis 

 edulis, Natica monilifera, Nassa incrassaia, Ostrea edulis, 

 Patella pellucida, Pecten maximus, Pholas crispata and 

 Candida, Purpura lapillus, Bissoa cingillus and striata, 

 Saxicava arctica and rugosa, Scaphander lignarius, Skenea 

 planorhis, Solen ensis, Syndosmya prismatica. Tapes pul- 

 lastra, Thracia distorta, Trophon clathratus and murlcatus, 

 Velutina Icemgata and Venus casina. Many of our naked 

 Mollusks take their place here. 



V. Peculiarly British may be styled the assemblage of 

 species little known elsewhere, or even unknown out of our 

 own seas. The list is considerable but very fallacious, 

 since it is swelled by minute or critical forms, that in all 

 probability enjoy a wider range, but have as yet escaped 

 observation on stranger shores. In this category we may 

 place many of the Odostomiw and Montacutee, hitherto un- 

 recognised on other coasts than our own. Every year dis- 

 covers that the parentage of some cherished species is not 

 so exclusively British as patriotic naturalists fondly ima- 

 gined. Excluding, however, all critical types or forms 

 liable from resemblance to others to be overlooked, the 

 following remarkable Testacea have not as yet been no- 

 ticed beyond our limits : — Assiminea Grayana, Astarte cre- 

 hricostata (probably arctic), Bucciiium fusiforme, Fusus 

 Berniciensis, Fusus Turtoni (the three last will probably 

 prove to be members of a more northern Fauna) ; the species 

 of Jeffreysia, Lepton Clarhiw, Megathyris cistellula, Natica 

 Kingii (probably arctic) ; Oiina otis, Pecten niveus, Pro- 



