MUREX RUDIS. 123 



It corresponds in form with a specimen of Murex. rndis, Borson, from the 

 Miocene of Touraine which I have received from M. Dollfus, and with that figured 

 bj Homes ; althougli none of the ribs are so varicose as in the latter, it may be, I 

 think, a water-worn variety of that species. Mr. Alfred Bell says it is the same as 

 the St. Erth shell described by him as Murex rudis. 



Most of the Manx fossils given in the lists published by Prof. Kendall in 

 189-t {op. elf.), and more recently by Mr. Lamplugh in his Survey Memoir, are 

 of a comparatively recent and northern character, and are believed by those 

 observers to owe their present position to the action of the glacial ice moving along 

 the bottom of the Irish Sea. An examination of the collections of mollusca from 

 the Manx Drift, however, reveals the interesting fact that they contain a group of 

 shells of a different character, some of them beautifully perfect, which are not of 

 Pleistocene age, having an affinity rather with Pliocene or even Miocene forms. 

 Separating these from those of a more recent type with which they are associated, 

 we have a fauna which does not altogether agree with that of any recognised 

 British horizon. It contains certain species characteristic of the Crag deposits of 

 East Anglia or of Iceland, but contains also some forms wdiich neither I nor the 

 specialists I have consulted have been able to identify wntli any hitherto described 

 or figured. 



These facts, however, are not necessarily antagonistic to the view taken by 

 Prof. Kendall and Mr. Lamplugh of the morainic origin of the Manx beds. 

 Fossiliferous deposits older than the Pleistocene may have existed formerly at the 

 bottom of the Irish Sea, the Manx fauna in that case possibly containing shells 

 derived from more than one source.^ 



Mr. Lamplugh considers that the conditions of the sea bottom surrounding 

 the Isle of Man may date back to late Pliocene times, and that this mixed fauna 

 and the presence of northern species imply a changing climate {o]). ctf., p. 389). 



The species which seem specially to represent a pre-Pleistocene fauna, none of 

 them being known living, are as follows : 



*Nassa consociata, var. brevis. Searlesia costlfer, var. monensis. 



*Nassa elegans. Searlesia Forbesi. 



*Nassa granulata, var. (imcilis. Searlesia Harrisoni. 



* „ „ var.fenestrata. Sea^-lesia Lundgrenii. 

 Nassa Kermodei. Searlesia Nordmanni. 

 Nassa monensis. Searlesia Oyeni. 

 Nassa reticosa, var. costata (JV. serrata of Prof. *Si2)ho curtus, var. exilis. 



Kendall). *Siplw menapiie. 



* ,, ,, var. lineata. *Sipho toriuosus, var. lirata. 

 Murex rudis. JFuszis longiroster. 

 Ocinehra tortuosa, var. minor. *Cerithium tricinctum. 

 Trophon Lamphighi (T. muricatus of Survey Memoir). 



1 Prof. Kendall has alluded to the mixed character of the Manx shells, which he says is different 

 from the natural grouping {op. cit., p. 432). 



