DENUDATION OF THE WEALDEN STRATA. 407 



belonging to the orders Diptera, Neuroptera, Hemiptera, 

 Orthoptera, and Coleoptera, and Crustacea belonging to the 

 genera Archceoniscm and Cypris, with shells of Cyclas, Ostrea, 

 and Paludina, and several small fishes, which he has figured 

 and described in his valuable Monograph on Fossil Insects. 

 The gigantic reptiles which characterise the wealden of Kent 

 and Sussex are absent from the "Wiltshire beds, but the 

 latter abound with many interesting forms of entomoid 

 articulata, of which no trace has been found in the south-east 

 of England. 



DENUDATION or THE WEALDEN. In conclusion, we have 

 to direct the student's attention to the evidences of denuda- 

 tion, so extensively presented throughout the wealden and 

 the cretaceous groups. The removal of the chalk, and 

 probably of the tertiary strata ; the abrasion of the wealden 

 beds ; the proofs of displacement and fracture which they 

 present; the anticlinal axis exhibited throughout a con- 

 siderable part of their range ; the fissures, which extend at 

 right angles to the anticlinal line, and which form the pre- 

 sent drainage of the district, constituting the beds of the 

 rivers Arun, Adur, Ouse, and Cuckmere ; these, with other 

 facts of a like nature, prove that these strata have under- 

 gone upheaval and disturbance on the most extensive scale, 

 at a comparatively recent period, probably during the ter- 

 tiary epoch. 



EXEECISES 



ON THE WEALDEN FORMATION. 



1. Explain the derivation of the term weald. 



2. Name the authors and collections of fossils. 



3. Mention its most important characteristics. 



4. Describe the geographical distribution of the wealden. 



5. Describe the general classification of its strata. 



6. Mention the most important localities of its occurrence. 



