,8^. NOTES AND COMMENTS. 405 



the subsequent uncovering by erosion of ancient bays and promon- 

 tories that marked the margins of Carboniferous seas. Later on, 

 extensive Permian rocks were laid down in inland seas. 



The features marked out in the Carboniferous area prior to the 

 Cretaceous covering are nowhere very striking ; the hills recently 

 uncovered are broad, flat-topped, and gently undulating. Thus, when 

 the Cretaceous period began in Texas, it found a low-lying land of 

 Carboniferous and Permian strata, undulating and nearly at its base- 

 level, and an older Palaeozoic highland district considerably diversified, 

 but not distinctly mountainous. Upon this area the encroaching sea 

 commenced the deposition of sands and conglomerates ; then, with 

 more complete submergence, followed higher beds of deeper water 

 origin. This basal Cretaceous deposit is not an ordinary beach con- 

 glomerate, for it contains many limestone pebbles, and the matrix, 

 fully one-half its bulk, is limy matter. The beds appear to have 

 been formed from the hurriedly worked over soils and land debris, in a 

 rapidly encroaching sea. Over the Permian strata they are red, 

 agreeing with the colour of the underlying rocks. 



The old Palaeozoic land at present seldom reaches an elevation 

 above 2,000 feet, and at i,goo feet traces of the earlier Cretaceous 

 beds have been found. The higher Cretaceous beds indicate deep- 

 water conditions ; they include thin beds that have been traced over 

 hundreds of square miles, and a great thickness of true chalk. Their 

 aggregate thickness is several thousand feet. These facts, taken in 

 conjunction with the absence of littoral characters in the higher 

 Cretaceous beds, and with the present dip of the strata in relation 

 to the older rocks, indicate that all the higher ground must have 

 been covered. The central highland region of Texas is at present 

 much more elevated than the uppermost Cretaceous beds to the 

 south-east'; it'was probably the first area to be upraised, and to suffer 

 denudation, so that the streams now have adjusted themselves to the 

 channels of the ancient watercourses. 



With regard to " The Texan Permian and its Mesozoic Types 

 of Fossils," we may state that a short memoir with the title just 

 given has been published by Mr. Charles A. White {Bulletin U.S. 

 Geological Survey, No. 77, 1891). Thirty-two species of Invertebrata 

 are recorded, and some of these are figured in four plates. The 

 species show a commingling of Carboniferous and Mesozoic forms. 



" A Severe Critic." 



In a pamphlet, printed for the author, and entitled " The Geo- 

 logical Map of the United States, and the United States Geological 

 Survey" (Cambridge, U.S.A., 1892), Mr. Jules Marcou has severely 

 criticised the conduct of the American Geological Survey. Rethinks 

 that " Ten or twelve years at most is a sufficient lapse of time to 

 execute all the researches in the field necessary to fill up the Geo- 



