84 



SCIENCE. 



[N. S. Vol. XV. No, 



basal coalbed, and the accompanying Ma- 

 honing sandstone, as well as the Red bed 

 series with its included crinoidal limestone, 

 from the Pennsylvania line to West Vir- 

 ginia. The results of this new work were 

 in close agreement with those arrived at by 

 the speaker in previous studies. The 

 speaker concluded with the following 

 corollaries : 



A. Some coal beds, limestones and sand- 

 stones may be followed for hundreds of 

 miles. 



B. Stratigraphy is superior to paleo- 

 botany in correlations. 



C. Paleobotany should be used merely 

 as an aid to stratigraphy. 



The paper brought out a warm discus- 

 sion, in which Professor Stevenson, Bailey 

 Willis, I. C. White and others participated. 



President Walcott read a telegram of 

 greeting from the Cordilleran section of 

 the Society, in session in San Francisco, 

 Cal. On motion of Professor Stevenson a 

 similar greeting was returned. 



The next paper read was : 



Correlation of the Coal Measures of Mary- 

 land: Wm. B. Clark and G. C. Martin, 

 Baltimore, Md. Read by Professor 

 Clark. 



The object of this paper was to show the 

 equivalency of the coal seams of Maryland 

 with those of .adjacent regions in Penn- 

 sylvania and West Virginia. The determin- 

 ation of this equivalency is based not only 

 on the parallelism of lithologic sequence 

 over wide areas, as shown both by the struc- 

 ture of the seams themselves and of the 

 intervening beds, but also on the fossilifer- 

 ous zones which have been found at numer- 

 ous points throughout this district. The 

 similarity of the chemical composition in 

 each vein over wide areas is also strikingly 

 shown. 



Local names, heretofore used by the 

 Maryland survey, were abandoned, and 



those used in Pennsylvania and West Vir- 

 ginia were adopted. The paper was dis- 

 cussed by I. C. White, J. J. Stevenson and 

 Bailey Willis. 



Areal Distribution of the Potomac Group 

 in Maryland: W. B. Clark and A. 

 BiBBiNS, Baltimore, Md. Read by W 

 B. Clark. 



The lowest member of the Atlantic 

 coastal plain series is the Potomac group, 

 so named by W J McGee, who considered 

 it a single unit. The age of this group was 

 considered to be Cretaceous by paleo- 

 botanists, and Jurassic by Marsh and 

 other vertebrate paleontologists. The 

 authors have described a fourfold division 

 of the Potomac into Patuxent, Arundel, 

 Patapsco and Raritan beds, and indicated 

 the distinctive characters of each. The areal 

 distribution, which varies for the different 

 members, was briefly discussed by the 

 speaker. Marsh found Dinosaur remains 

 in the Arundel, which, with the underlying 

 Patuxent beds, is Jurassic. The plant re- 

 mains were found in the upper or Raritan 

 beds, and these are cretaceous. The lower 

 members gradually die out northward, the 

 Patuxent and Arundel not occurring in 

 New Jersey, though some of the lower 

 members appear to be present in Pennsyl- 

 vania. The disappearance is due to a 

 northward transgression of the sea and a 

 consequent overlap of the newer upon the 

 older beds. The paper was briefly dis- 

 cussed by Professors Hopkins and Holmes, 

 and questions answered by Professor Clark. 



On some Joint Veins: G. K. Gilbert, 



Washington, D. C. 



A limestone stratum between beds of 

 Cambrian shale from western Utah shows 

 innumerable veinlets of the segregation 

 type. In a small hand specimen passed 

 around, 180 veins were counted. These be- 

 long to 22 systems, which are grouped in 

 two groups, the minor of which is aligned 



