2o6 OUR COMMON BRITISH FOSSILS. 



that account) have not been found in rocks of older 

 formation than the Lower Oolite. There we get a 

 generic form, named by Dr. H. Woodward Palicena- 

 chits. The long-bodied Crustacea {Macrura) had 

 appeared in the stage of creation before the end of 

 the Primary period, as Anthrapalcemon — the Phyllopods 

 (a lower group) having preceded them. 



In many English localities the fossil Crustacea are 

 very beautifully preserved, and are unquestionably 

 among the gems of the cabinet when properly worked 

 out. In the Oolitic and Cretaceous rocks we have 

 the well-known generic type Eryo7i, not at all uncom- 

 mon. The chalk of Hertfordshire has yielded to a 

 friend of mine (who was geologically inclined, and 

 wanted a " hobby ") a number of nezv forms of fossil 

 crayfishes. The real fact was — they wanted hunting 

 up. When the student has learned to recognize crus- 

 tacean structure, and he sees a bit of it cropping out 

 in the chalk, he must work away with his pocket- 

 knife and tooth-brush until the whole of the probably 

 buried-up crustacean is developed. Chalk is a capital 

 rock for allowing of this ; the harder Oolitic lime- 

 stone is not so easily persuaded to give up its dead. 



When we came to the Tertiary formations, espe- 

 cially to the Eocene — or rather, the London Clay 

 representative of that interesting formation — the 

 higher-developed fossil crustaceans are not uncom- 

 mon, and, in places, even plentiful. The London 

 Clay of the Isle of Sheppey is a sort of crustacean 



