554 PROF. PAVLOW ON THE CLASSIFICATION OP THE [Aug. 1896, 



I am well aware that the present is a vague and incomplete 

 sketch of the subject, but it may serve to turn the attention of my 

 co-workers to the places and questions especially interesting from 

 this point of view, and thus lead in the future to a more satisfactory 

 grouping of the geological events of the period. From a broader 

 standpoint it shows, too, how in different countries the subdivisions 

 of a series of beds may replace one another in regular sequence,, 

 allowing us to follow out the ever-changeful development of the 

 earth's surface from one epoch to the next. 



EXPLANATION OF PLATE XXVII. 



[The figures are all of the natural size.] 



Figs, la, lb, I c. Aucella volgensis, Lahus. Lower Greensand, Donnington. 

 „ 2 a, 2 b. Aucella volgensis, var. radiolata. Lower Greensand, Don- 



nington. 

 „ 3 a, 3 b, 3 e. Aucella Keyserlingi, Lahus. Tealby Series, Claxby. 



All the specimens are preserved in the Woodwardian Museum at Cambridge. 



Discussion. 



Mr. Strahan remarked that this paper was of especial value at 

 the present time, for English geologists had so far failed to 

 establish a satisfactory separation of the Jurassic and Cretaceous 

 systems. The correlation of the North of England with the South 

 was still a matter of doubt, while even in the classic region which 

 had furnished the names of Wealden, Purbeck, and Portland the 

 upper limit of the Jurassic was quite uncertain. The Purbeck strata, 

 first classed as Oolitic, were transferred by Webster and Fitton 

 to the Wealden, reinstated as Oolitic by Forbes, and restored to the 

 Wealden by Topley, while recently, seventy years after the question 

 first arose, we have been assured by three different observers that 

 the reptiles, fishes, and plants of the Wealden possess undeniable 

 Oolitic affinities. Under such circumstances, a communication from 

 a geologist of the world-wide experience of Prof. Pavlow promises to 

 be of the utmost assistance to us in arriving at the most suitable 

 grouping. 



Mr. Teall said that he was sure that all present regretted the 

 absence of the Author. He could not discuss the paper, but he 

 should like to give expression to the pleasure which he had felt in 

 listening to it. Papers dealing with comparative stratigraphy of 

 wide areas were rare at the Society, and he thought that the present 

 one would therefore be cordially welcomed. He had not previously 

 met with the terms ' hydrocratic ' and ' geocratic,' but they seemed 

 to him of great value. He had often felt the want of such terms. 



Mr. Lampltjgh expressed the extreme gratification that he felt at 

 being made the medium for conveying this important paper to the 

 Society. Whether the proposals of the Author with respect to the 

 classification receive general acceptance or not, there could be no 

 doubt of Prof. Pavlow's qualifications for the task, and the infinite 



