158 PROCEEDINGS OF THE ACADEMY OF [1895. 



About this time a change clue to some extraneous causes occurred. 

 Whatever the cause of this change may have been it induced a 

 flexing, or gentle undulation, involving the whole series from the 

 middle of the Marine beds backward to and including a portion of 

 the upper Cretaceous. This flexing apparently brought the long 

 period of subsidence to an end. The whole of the lower Marine 

 beds were brought to the surface and a period of elevation began. 

 During this stage the last 250 feet of the Marine beds were deposited 

 in comparatively shallow water and along a sandy floor sloping 

 gently seaward. 



With the close of the Marine beds the elevation ceased, and for a 

 long period the land remained stationary. During that time erosion 

 was working actively. The sea to the southward was cutting the 

 sloping shores and carving them in many places into steep cliffs ; the 

 rivers were widening and deepening their channels, carrying their 

 burdens of debris seaward and depositing them in the shallow waters 

 of the Gulf. Here these materials were sorted and arranged into 

 banks of sand with muddy intervals, gradually filling up the 

 shallow shore waters. Again we find the marine waters being 

 gradually closed out, the streams gathered into sluggish bayous 

 and the whole drainage system disarranged. Fresh and salt waters 

 met and mingled in the bayous and occasional inundations covered 

 the whole region. Marsh plants, grasses, reeds and palmettos 

 gradually overspread the wide domain now occupied by the Yegua 

 clays. Again we have a period of slow subsidence and a return to 

 very similar conditions of life as those of lignitic times. The bayous 

 were probably wider, deeper and clearer than those of the lignitic 

 stage and life appears to have been more plentiful. The alligator 

 lived in the marshes and marine shells such as Tellina mooreana Gb. 

 Turritella nasuta var. houstonia Harris, Natica recurva Aid., and 

 Nucula magnified Con., found a means of surviving in some of the 

 sandy deposits along the lines of the greater water courses. 



The time of depression continued long enough to deposit extensive 

 beds of lignite clays and sands to a total thickness of 1,000 feet. 



If we might suppose a slight uplifting of the land areas to the 

 north and consequent tilting of these beds towards the sea we would 

 then find a considerable portion of these marshy areas submerged by 

 deeper and clearer water, a deposition of sands and clays going on 

 and :i partial return to marine conditions of life. The newer 



