26 i Robert Bell — Land Shells in the Med Crag. 



and the shell did not appear to the writer to quite agree, either with 

 the engraving or description given of that species by Mr. Wood, nor 

 did it appear to have relation to H. rufescens, to which Dr. Jeffreys 

 had assigned H. Rysa as a variety ; but after a careful examination 

 of a lai'ge series of European Helices in the cabinet of Mr. J. H. 

 Ponsonby, it was recognized as identical with H. lens, a shell that 

 has an entirely southern range in Europe, occurring only in Morea 

 and the Greek islands (Pfeiffer) ; in this identification both Dr. 

 Jeffreys and Mr. Ponsonby concur. 



Selix incarnata, Miiller. Figured, Moquiti-Taiidon, Moll, de France, pi. 16, fig. 

 6 and 7. 



This shell was found by the Prince of Mantua (Mr. Groom- 

 Napier), in the course of some extensive excavations made at Walton, 

 in 1882, which resulted in the fine collection of Ked Crag Mollusca 

 shown at the Fisheries Exhibition last year. It is not perfect, but 

 the mouth, first whorl, and base of the shell remain, and seem quite 

 identical with this continental species; hitherto this shell has not 

 been noticed earlier than the Copford deposits, where it is associated 

 with several others now extinct in Britain. 



Helix lactea, Muller. Figured, Eeeve, Con. Icon., vol. vii. pi. 147, fig. 955a. 



A fine example nearly perfect was found by the writer last summer ; 

 the first and second whorls, the base and mouth of the shell, are quite 

 perfect, and it retains its bands of brown colour ; in a recent state 

 this species is limited to the Mediterranean shores of Spain, France, 

 and North Africa, where it is plentiful ; it was compared with a 

 large series from various localities, and resembles an Algerian form 

 more than any other ; a fragment of this species was also found 

 in the Upper Ked Crag bed by the same collector. 



A comparison of the present geographical range of the above 

 three recent species with that of the land shells of the Butley beds 

 will exactly carry out the deductions which can be made from a 

 similar comparison with the Marine faunas of the two places. At 

 Walton it is mainly southern ; at Butley the number of northern, 

 American, and even arctic shells is very considerable — such species as 

 Amaura Candida, Cardium Greenlandicum, Trophon scalar if or me, Natica 

 Greenlandica, and several of those species of Pleurotoma which only 

 occur in cold latitudes, indicate a northern character. But the 

 presence or absence of certain species in any given bed of Crag (the 

 fauna of which is by no means worked out yet) is not such good 

 evidence as the numerical preponderance or scarcity of the in- 

 dividuals of common forms. The immense numbers of cold area 

 shells, such as Tellina obliqua, at Butley, with its extreme scarcity 

 at Walton, where Natica multipunctata (extremely scarce at Butley), 

 is perhaps the most prevalent and representative form, whose range 

 is entirely southern, will show a fairly characteristic difference in the 

 two deposits. The whole evidence shows the very considerable 

 change which came over the character of the Mollusca of the British 

 Seas, indicating the gradual lowering of temperature and the setting 

 in of arctic currents, which had already begun to take place in the 

 earliest times of the Ked Crag. 



