66 Bibliographical Notices. 



dilBFerences between the species described by Jeffreys in his second 

 volume and those of Forbes and Hanley : — 



Species added. Species excluded. 



Argiope decoUata, Ghemn. Hypothyris psittacea, Chemn. 



capsule, Jefr. Anomia aculeata, MUlL 



Pecten Testae, Bivona. striata, Lov. 



Lima Sarsii, Lov. Pecten uiveus, Macg. 



elliptica, Jeffr. Nucula radiata, F. ^ H. 



Limopsis aurita, Brocchi. Astarte elliptica, Brown. 



Area obliqua, Phil. crebricostata, Forbt*. 



Lepton sulcatulum, Jejffr. arctica, Gray. 



Axinus Croulinensis, Jeffr. Mactra elliptica, Brown. 



Cardium papillosum, Poli. Tellina proxima, Brown. 



Three of the additions made to our fauna — Argiope decoUata, 

 Lepton sulcatulum, and Cardium papillosum — are Mediterranean 

 species, which have hitherto only occurred in the extreme south of 

 the British Islands, off Guernsey ; on the other hand, Lima Sarsii, 

 Area obliqua, and perhaps Limopsis aurita are Scandinavian form! 

 which have now been met with in Shetland ; while the four remain- 

 ing shells have more extended range on our coasts. 



The especial attention which has been paid of late years by geo- 

 logists to the more recent deposits of our islands, and especially to 

 those contemporaneous with and subsequent to the glacial epoch, 

 has led to a great advance in knowledge respecting the connexion of 

 our present fauna with that of the latest periods of geological time ; 

 nor have these investigations been confined to the land. The dredge 

 has made known to us the fact that on the sea-bottom all round our 

 shores there are lying, mixed with the dead and living examples of 

 our present fauna, the shells of various MoUusca, often remarkably 

 fresh in appearance, which have apparently ceased to live in our 

 waters. It is often a matter of extreme difficulty to determine 

 whether a species dredged only in a dead state be recent or fossil ; 

 and hence it happens that Hypothyris psittacea, Astarte crebri- 

 costata, A. arctica, and Tellina proxima, together with Mya Udde- 

 valensis, Margarita cinerea, Margarita (Skenea) costulata, Natiea 

 clausa, Astyris Holbdllii, Trophon scalariformis, &c., have been in- 

 troduced among our Mollusca, but are now believed to be extinct 

 representatives of more northern existing species, which once lived 

 associated with our recent Mollusca, but gradually died out as the 

 temperature of the waters which surround our coasts increased, and 

 are now no longer to be found living in a latitude so far south. 

 ^ Most conchologists will also be ready to acquiesce in the suppres- 

 sion of Anomia aculeata and A. striata as distinct from A. ephip- 

 pium and A. patelliformis ; but what shall we say to Pecten niveus 

 being merged in P. varius, Nucula radiata in N. nucleus, Astarte 

 elliptica in A. sulcata, and Mactra elliptica in M. solidal In 

 writing on the first of these changes, Mr. Jeffreys says :— " I fear 

 that some of my conchological friends will be terribly shocked at my 



