Geology. 593 



4. Maryland Geological Survey (Lower Cretaceous); Balti- 

 more, 1911. 8vo, pp. 622 and 117 plates. — The fine series of 

 reports on the Geology and Paleontology of Maryland, of which 

 the volumes on the Eocene, the Miocene, and the Plio-Pleistocene 

 have hitherto appeared, is here continued in a handsome fourth 

 volume on the Lower Cretaceous, or Potomac Group, of the 

 Maryland- Virginia area. The work forms one of the primary 

 units in the elaboration of the continental geology, dealing fully 

 and thoroughly as it does with the type sections for the Lower 

 Cretaceous of the Atlantic border at their maximum of lithologic 

 and paleontologic differentiation. 



The Potomac Group is described physiographically by Messrs. 

 Clark, Bibbins and Berry as a series of some 600 to 700 feet 

 of estuarine fluviatile deposits resting on the old crystalline floor 

 or "Weverton peneplain" on which important present-da}^ drain- 

 age lines were already established. In general harmony with the 

 continental border warp of the floor, the Potomac surface has a 

 lessening slope to the southeastward. Three subdivisions each 

 clearly separated by nonconformity are finally established, the 

 Patuxent, the Arundel and the Patapsco ; Patuxent- Arundel time 

 being equivalent to the Neocomian and Barremian, and Patapsco 

 time to the Albian following an Aptian hiatus. 



The Arundel reptilia, mainly including the series of dinosaurians 

 collected by Hatcher and studied by Marsh, are revised and re- 

 illustrated by Professor R. S. Lull, of Yale L T niversity, who 

 finds a distinct correlation with the Morrison of the West. 



The limited invertebrate fauna of the Arundel and Patapsco is 

 described by Professor Clakk ; while the main body of the 

 volume is occupied by Dr. E. W. Berry in a restudy and illustra- 

 tion of the Potomac flora. 



Following a survey of the Lower Cretaceous floras of the world 

 the Potomac plants are given a far more usable treatment than 

 has hitherto been available to paleobotanists. For the Cyca- 

 deoidea types of the Patuxent (?) the diagnoses of Ward are con- 

 veniently retained. But it is held that the view of Wieland and 

 others that such plants are very near the angiosperm (Ranales, 

 etc.) line of descent "overlooks the wide difference in structure 

 throughout the vegetative body, where the characters are much 

 more conservative, and furnish a much safer clue to filiation than 

 do the reproductive parts, especially Avhen of the indicated plas- 

 ticity of those of the Cycadophytes." The text is throughout 

 illustrated by clear figures, and the excellent heliotypes of the 

 early dicotyls of the Patapsco, the oldest of the continent, must 

 hold high interest for botanists. g. r. w. 



5. A Method of Removing Tests from Fossils ; by S. S. 

 Buckman (communicated).— A note under this title appeared in this 

 Journal, August, 1911 (vol. xxxii, p. 163). By some accident, in 

 the second line of the second paragraph the epithet "close-grained" 

 was printed " coarse-grained." The present note is designed to 

 call attention tothis small error. A coarse-grained core is not at all 



