Ch. xyih.] fossils of the wealden group. 



261 



the vegetable productions on which they feed, but do not chew them. 

 Their teeth frequently present an appearance of having been chipped off, 

 but never, like the fossil teeth of the Iguanodon, have a flat ground sur- 

 face (see fig. 304, b), resembling the grinders of herbivorous mammalia. 



Tig. 803. 



Fig. 304. 



Fig. 303. a, b. Tooth of Iguanodon Mantelli. 

 Fig 304. a. Partially worn tooth of young individual of the same. 

 b. Crown of tooth in adult, "worn down. (Mantell.) 



Dr. Mantell computes that the teeth and bones of this species which 

 passed under his examination during twenty years must have belonged to 

 no less than seventy-one distinct individuals, varying in age and magni- 

 tude from the reptile just burst from the egg, to one of which the femur 

 measured 24 inches in circumference. Yet, notwithstanding that the 

 teeth were more numerous than any other bones, it is remarkable that it 

 was not until the relics of all these individuals had been found, that a 

 solitary example of part of a jaw-bone was obtained. More recently 

 remains both of the upper and lower jaw have been met with in the 

 Hastings Beds in Tilgate Forest. Their size was somewhat greater than 

 had been anticipated, and Dr. Mantell, who does not agree with Professor 

 Owen that the tail was short, estimates the probable length of some of 

 these saurians at between 50 and 60 feet. The largest femur yet found 

 measures 4 feet 8 inches in length, the circumference of the shaft being 

 25 inches, and, if measured round the condyles, 42 inches. 



Occasionally bands of limestone, called Sussex Marble, occur in the 

 "Weald Clay, almost entirely composed of a species of Paludina, closely 

 resembling the common P. vivipara of English rivers. 



Shells of the Cypris, a genus of Crustaceans before mentioned (p. 31) 

 as abounding in lakes and ponds, are also plentifully scattered through the 

 clays of the "Wealden, sometimes producing, like plates of mica, a thin 

 lamination (see fig. 307). Similar cypris-bearing marls are found in the 

 lacustrine tertiary beds of Auvergne (see above, p. 199). 



