TRANSACTIONS OF SECTION C. 635 



nation by Professor D. Lovisato. A memoir on tbe subject by Professor F. 

 Bassani had lately appeared (' Atti R. Accad. Sci. Napoli,' Series 2, vol. iv., 

 Mem. No. 3, 1891), and tbe present communication contained only brief supple- 

 mentary observations. In addition to the Selachian genera and species recognised 

 by Bassani, the author identified teeth of Scymnvs, O.vyrhina Desori, Galeus, 

 Aprionodon, and probably Vhysodon, besides dermal scutes of Trygon. The 

 collection comprises no evidence of ganoid fishes, and most of the remains of 

 teleosteans are too imperfect even for generic determination. Traces of Scom- 

 beroids and Labroids occur, and there is evidence of a new species of the Berycoid 

 Holoceyitrum. Teeth of Ckrysophrys, Sargus, and other common Mediterranean 

 genera are abundant ; and a few detached yellow teeth represent an indeter- 

 minable species of Balistei, 



5. Evidence of the Occurrence of Pterosaurian and Plesiosaiman Reptiles 

 in the Cretaceo^is Strata of Brazil} By A. Smith Woodward, F.G.S. 



The author exhibited and described two examples of the articular end of the 

 quadrate bone of a Ptei'odactyl, and one imperfect propodial bone of a Plesiosaur^ 

 discovered by Mr. Joseph Mawson, F.G.S. , in the Cretaceous Formation near 

 Bahia, Brazil. Though not generically determinable, the fossils are of much 

 interest as being the first evidence of the reptilian orders in question from the 

 Mesozoic deposits of South America. 



6. The Cause of Monoclinal Flexure. By A. J. Jukes-Beowne, F.G.S. 



Folds of the ordinary arch and trough type are generally ascribed to the in- 

 fluence of lateral pressure ; but it is not easy to see how a monoclinal flexure 

 which appears in section as a flexure connecting two horizontal bars of strata can 

 have been produced by direct lateral pressure exerted at tbe ends of the bars. 



The author suggests that monoclinal flexuring is a structure impressed upon a 

 horizontal series of uncompressed strata by the displacement of a subjacent mass of 

 faulted and flexured rocks, tbe lateral compression of the deep-seated mass result- 

 ing in the vertical uplift of certain portions of the ' cover.' If a series of stratified 

 rocks rests in a horizontal position on a mass of ancient rock, which has been com- 

 pressed, indurated, flexured, and faulted before the deposition of the upper series, 

 it is supposed that tbe lower series of rocks would give way under lateral pressure 

 along tbe pre-existing faults, and that the blocks which lie between upward diverg- 

 ing faults would be forced to move upwards, carrying with them those tracts of 

 the ' cover' which rest on them. It is evident that these tracts would be divided 

 from those resting on blocks defined by downward diverging faults by faults or 

 monoclinal flexures, the production of a fracture or a flexure depending partly on 

 the thickness and pliability of the strata forming tbe cover and partly on the 

 amount of local uplift. It is conceivable that tbe displacement might take place 

 partly by faulting and partly by flexuring, and that what was a fault near the 

 plane of unconformity might pass upward into a flexure. 



Tbe writer desires criticism on the above suggestion, especiallj' from those who 

 will have a chance of seeing the grand monoclinal flexures of the Colorado region 

 during the excursion of the approaching International Geological Congress. 



7. Note on an Undescribed Area of Lower Greensand, or Vectian, 

 in Borsetshire. By A. J. Jukes-Browne, F.G.S. 



[Communicated by permission of the Director-General of the Geological Survey.] 



A recent examination of the ground below the escarpment of tbe Chalk in 

 North Dorset has revealed the existence of a tract of Vectian or Lower Greensand 

 which had not previously been suspected. Reference to the Geological Survey 



" Published in extenso in Ann. Mag. Nat. Hist. [6] vol. viii. pp. 314-317. 



