256 OUR COMMON BRITISH FOSSILS. 



exchange for those of his own neighbourhood. Or 

 let him cultivate the acquaintance of the nearest 

 stone-mason's yard, the proprietor whereof will set 

 him up with plenty of "rotten stuff," unworkable 

 because of the hollows and casts of fossil shells, but 

 dearer to the young geologist than a gold-mine on 

 that account ! Fragments of Portland Oolite may 

 always be got in any large stone-mason's yard, and 

 they contain an abundance of fossil (casts), Nerinceay 

 Cerithium, and Trigonia^ all of which are usually casts 



Fig. 237. — Trigotiia inargaritacea (Australia seas). 



of the interiors of these shells ; so they have a very 

 different appearance from the more gracefully shaped 

 and ornamented exteriors. 



Tourists in the north-west of Scotland will find 

 some interesting and varied geologizing in Western 

 Scotland and the Hebrides ; and in various places 

 the Lias beds yield fossils, as along the Sound of 

 Mull, Tobermory, the Isle of Skye, Eigg, Muck, etc., 

 where there are fragmentary patches and outliers of 

 once very extensive Lias and Oolitic strata, which 

 probably extended from continuous fossilferous strata. 



