of the Vale of Wardour. 255 



Mr. Woodward gives no reason for his grouping of the beds ; he 

 does not dispute our record of G. fasciculata, though he does not 

 quote it, and here, therefore, the question of consistency certainly 

 does arise, for the accepted divisions of the Purbeck Series are based 

 on the successive appearance and prevalence of the three species of 

 Cypridea, C. purbecJcensis, G. granulosa, and G. punctata, and any 

 vp-riter who accepts this basis of classification should be consistent 

 and should not group beds as Lower Purbeck when their prevalent 

 Cyprid is G. granulosa. 



If Mr. Woodward preferred to adopt some other criterion he might 

 have explained his reason for abandoning that of the Cyprides ; it 

 may be only a coincidence that his Lower Purbecks include all the 

 so-called ' Lias beds,' but it is conceivable that he preferred to group 

 together beds of similar lithological character rather than be fettered 

 by the range of a single small Crustacean. In that case, however, 

 " to be consistent " he should have made a similar alteration in the 

 grouping of the Lower and Middle Purbecks of Dorset; it is not 

 satisfactory to have one method of classification for Dorset and 

 another for Wiltshire. 



I see no reason for any departure from Forbes' convenient 

 method, and consequently I maintain that the Middle Purbeck 

 group in the Vale of Wardour is much thicker than Mr. Woodward 

 makes it. In his table on p. 267 he gives the thickness of Middle 

 Purbeck Beds as only 12 feet, but he has apparently based this 

 estimate on his section of the railway-cuttings west of Dinton 

 given on p. 274. In this section he has referred the lowest beds 

 exposed to the Lower Purbeck, but I believe he is quite mistaken 

 in such a correlation. His ' brown sandy limestone ' No. 1 repre- 

 sents the ' shaly limestone,' which he takes as the base of the 

 Middle Purbeck in Teffont quarry, and the whitish limestones above 

 are the equivalent of the ' White Bed ' in that quarry. I write 

 confidently of this because there are similar beds in the next cutting 

 on the railway (south of Teffont), and their combined thickness 

 there (4 feet) is rather more than the beds on the same horizon 

 west of Dinton (where Mr. Woodward's measurement makes them 

 3 feet 9 inches). 



With the above correction, Mr. Woodward's restricted Middle 

 Purbeck would be about 15 feet thick, but when the group is 

 carried down to the base of the shale below the ' flagstone ' in the 

 Teffont quarry, as I consider it ought to be, its total thickness is 

 a little over 22 feet.^ 



3. The Upper Purheck Group. — The existence of this group in the 

 Vale of Wardour was denied until the publication of our paper in 

 1894, though the Dinton cutting, in which the lower part of the 

 group is exposed, had been open for many years, and if anyone had 

 taken the trouble to collect Cyprides from the beds and to submit 

 them to an expert like Professor Eupert Jones, he would have 



1 I admit an error iu our computations of thickness on p. 66 of Quart. Journ. Geol. 

 Soc, vol. L, clue to our having counted in twice beds which we now recognize to be 

 the same. 



