1872.] MEYEE WEALDEN AND " PTJNFIELD FORMATION," 251 



has been since, to some extent, confirmed ; for I have learnt that a 

 fossil lobster similar to those of Atherfield had been some time pre- 

 viously obtained from this very stratum. The specimen is now in a 

 small local museum at the village of Corfe, in the Isle of Purbeck, 



The hard thin band of ironstone-grit at the base of these clay- 

 beds did not appear to contain fossils ; it represents unquestionably 

 the stratum c described by Mr. Judd as forming the base of the so- 

 caUed "Punfield formation" at Worborrow Bay* to the west of 

 Swanage, and in which marine fossils were recognized by Professor 

 E. Forbes. 



I examined most carefully the whole of the exposed strata from 

 the " Marine band " upwards to the junction of the Keoeomian sand 

 with the Gaiilt, and obtained many fossils from the two principal 

 shell-beds. 



The " Cypridiferous shales with bands of limestone " containing 

 freshwater fossils, described as occurring at the top of the " Punfield 

 beds," I could not discover, although they may possibly be present 

 in that position. The *' beds of sandstone containing Cyprules and 

 casts of Gyrena " I could not find ; and I may state at once that in a 

 two days' search I failed to find either a smgle valve of Cypris or 

 the faintest evidence of any freshwater fossU in any portion of the 

 series ; and I understand that Mr. Judd himself was equally unsuc- 

 cessful. 



It is true that the thin-bedded sands and clays with lignite and 

 fragments of carbonaceous matter so common in this section have 

 some resemblance to freshwater deposits, but not more than the 

 marine sands and clays with lignite of the Eocene Lower Bagshot 

 beds of Whitecliff" Bay, or even than some portions of the Lower 

 Greensand. 



But, it is said, the fauna of the Punfield beds proves their position 

 as a portion of the "Wealden. What is this fauna ? It is a semi- 

 marine or brackish -water fauna, the fauna of a shallow- water or 

 littoral deposit, and so far agrees with the condition of the strata. 

 But it is also a mixed fauna, composed of three elements, which require 

 to be considered separately. It includes first, a set of species peculiar 

 to the locality so far as the British strata are concerned ; it in- 

 cludes, secondly, a fauna scanty in species but individually numerous, 

 which belongs, as it were, of right to the Purbeck-Wealden area ; 

 and, thirdly, it includes a fauna extremely common in the Lower 

 Greensand. 



In the first of these groups I include a set of marine or brackish- 

 water mollusca peculiar to this locality and to the coal-bearing 

 strata of Eastern Spain ; and these, as I take it, are of no value 

 whatever in proving the position of the deposit, even though, as Mr. 

 Judd has so clearly shown, they prove its age. 



In the second group I include at most three or four species of 

 brackish-water moUusks ; but these are specially worth notice ; they 

 are a Cardium, a small Ostrea, a Corhula or Potamomya, and a 

 species of Mytilus. Now, in studying the fossils of the Purbeck- 



* Quart. Joiu'n. Geol. Soc. vol. xxvii. p. 216. 



T 2 



