J. C. Mansel-P ley dell — Geology of Dorset. 439 



sionally. At Osmington Mills, withiu less than a square mile, the 

 Upper Greensand is in contact successively with the Hastings Sands, 

 the Purbeck Beds, and the Kimmeridge Clay. Here the alternation 

 of fine clays and sands peculiar to the Swanage Beds with the coarse 

 drift of Worbarrow plainly reveals the swelling and subsiding of the 

 ancient river which covered them eastward. From the pi'esence of 

 iron the Rev. 0. Fisher considers the deposit to have been furnished 

 from the New Eed Sandstones of Devonshire. 



Of the gigantic reptiles of the Wealden age the Dorsetshire beds 

 produce two, Iguanodon Mantelli and Megalosaurus BucJclcmdi. Mr. 

 S. H. Beckles, F.R.S., describes in the Geological Journal, vol. xviii. 

 p. 446, casts of footprints in Swanage Bay occurring in two bands 

 of sand-rock of the usual tripodal shape, about fifteen inches long, 

 whicl) may be the footprints of a Wealden Dinosaur, or perhaps of a 

 Batrachian. 



The Flora of the Wealden contains ConifercB, Cycadece, aiid Ferns. 

 In 1855 the Gyrogonites (so named by Parkinson in 1822), spore- 

 vessels of the Chara, were found in the Hastings Beds of the Isle of 

 Wight, a genus common in the Tertiary strata, but not found before 

 this in the Secondary rocks. 



The variegated Wealden Clays and Sands are about 1800 feet thick 

 at Swanage, 725 at Worbarrow Bay, 660 at Mewps Bay, 462 on the 

 east side of Lul worth Cove, and 172 at Man of War Cove, showing 

 in a very remarkable manner the attenuation of the beds which takes 

 place westward ; this peculiarity is not restricted to the Wealden, 

 but extends to the Lower Chalk as well. 



The Purbeck Beds have been examined and mapped in great detail 

 by Mr. Bristow, and published in the works of the Geological Survey 

 of Great Britain. In Sheet 22 of the Vertical Sections every bed 

 is shown on a scale of 10 feet to one inch, with full lithological and 

 palaeontological descriptions. 



Lower Cretaceous or Neocomian. — Punfield beds. — A remark- 

 able bed, partly marine and partly of estuarine origin, lies at the top 

 of the Wealden Beds at Punfield, Worbarrow, and Mewps Bay. It 

 has long been known to geologists as differing from the freshwater 

 Wealden in mineral character, and in its animal remains, clearly 

 indicating the gradual return of marine conditions which continued 

 throughout the Cretaceous period. 



A marine band, 21 inches thick, rests on the variegated beds of 

 the Wealden, dipping due north at an angle of 65° ; Mr. Judd, who 

 has recently separated these beds from the Wealden Series, to which 

 they were before attributed, divides this marine bed into three parts, 

 the lower being a shelly Limestone, containing concretions of argil- 

 laceous Limestone, yielding Ammonites, Vicarya, and other marine 

 shells ; the middle portion is almost entirely made up of Oyster-shells 

 with a few dwarfed specimens of Gorbida and Cardium ; the upper 

 portion contains but few shells, and, like the middle, is mixed with 

 much carbonaceous matter. The narrow band is succeeded (upwards) 

 by a series of ferruginous sands, about 153 feet thick; its middle 

 portion is composed of ferrugineo-calcareous rock, with Oysters and 



