During Triassic and Jurassic Periods 191 



In papers by Wright (i-f-fii^) and Roberts {143:- 

 229) extensive lists are given of marine invertebrate organ- 

 isms in appropriate strata, but no mention is made of fishes, 

 reptiles or mammals, all of which were then abundant over 

 land or lacustrine areas. In contrast to this Judd in "The 

 Secondary Rocks of Scotland" {146: gj) not only lists 

 abundant and typical marine fossils from lower Jurassic 

 rocks of the Moray Firth region, he further emphasizes the 

 freshwater nature of many strata, which he correlates 

 with the Portland, Purbeck and Wealden of Anglo-French 

 areas. They agree also in showing, not unfrequently, alter- 

 nations of freshwater and marine beds with their ap- 

 propriate fossils. But for the former beds he habitually 

 uses the expression "estuarine," to which the writer would 

 take exception, and replace by the name lacustrine. For 

 wherever a careful discrimination is made, the so-called 

 "estuarine" beds contain only freshwater fossils, or these 

 rarely mixed with what evidently were washed-out and re- 

 deposited oyster shells. For in referring (p. 103) to an 

 "argillaceous type of estuarine strata" that is made up 

 largely of finely laminated clays, he states that these clays 

 "contain also thin bands of limestone, sometimes crowded 

 with shells of Cyrena^ Unio, and other freshwater bivalves, 

 sometimes with Paludina and other freshwater univalves, 

 and at others made up of dwarfed Ostreae and other marine 

 shells, crowded together in masses, and forming beds 

 exactly resembling the well-known "Cinder-beds" of the 

 Purbeck. In these clays, beds crowded with the valves 

 of Cyprides and Estheriae also occur, with veritable bone- 

 bands, made up of scales and teeth of fishes and bones of 

 reptiles. Not unfrequently these clays are crowded with 

 plant-remains; and interstratified with them occur beds of 

 lignite or coal, sometimes several feet in thickness, some of 

 which have been worked with success." 



"No one can examine these strata of the argillaceous 

 type without being at once struck with their resemblance to 

 those of the Purbeck formation, and also to those of similar 

 character which occur at the top of the Wealden in the 

 Isle of Wight and elsewhere, which I have described in 

 detail under the name of the Punfield Formation." 



