398 



SPECIAL GEOLOGY. 



contents of the different beds, implies that many changes of 

 condition took place during the deposition of the Purbeck 

 beds. Professor E. Forbes has recently examined the 

 organic remains of the three members of the Purbeck group, 



Fig. 278. Section in a Cliff east of Dulworth Cove, Dorset. 



displayed at Meup's Bay, Dorset, in a vertical section of 

 155 feet. To our previous information he has added some 

 important facts ; the Professor found that the upper, middle, 

 and lower Purbecks, are each marked by peculiar species 

 of organic remains ; these, again, being different from the 

 fossils of the Hastings sand and weald clay.* 



FIG. 279. Mantellia nidiformis. Brongniart. 



Upper Series. The highest of the three divisions is 

 purely a fresh-water deposit, about 50 feet in thickness, 



* Professor E. Forbes, on the Dorsetshire Purbecks. See also Sir C. 

 Ly ell's Manual (third edition) for much interesting matter on this subject. 



