208 PROCEEDINGS OF THE PALEONTOLOGICAL SOCIETY 



present line of outcrop and liave been since entirely removed by erosion. The 

 Genesee shale is the mud brought by a river from the south into Pennsylvania 

 and New York. The relationship of the two formations is that of replacing 

 overlap — the muds gradually advancing from the south over the limestone. A 

 recent study of the sections near Ithaca has furnished abundant evidence of 

 such replacement. 



A second paper on the classification of Silurian and Devonian corals 

 was then given nnder the following title. Discussed by A. W. Grabau 

 and the author. 



AMERICAN DIPIIYPHYLLOID CORALS 

 BY GEOKGE II. CIIADWICK 



{Abstract) 



A critical review of the half hundred specific names proposed for American 

 Silurian and Devonian corals of the genera Diphyphyllum, Diplophyllum, 

 Eridophyllum, Oraspedophyllum, Synaptophyllum, and their allies, with dis- 

 cussion of the synonymy and classification within the group thus indicated. 

 On the basis of well marked natural characters, it is shown that there are 

 several definite generic types passing current under the name Diphyphyllum 

 as broadly used, none of which are strictly referable to this European Car- 

 boniferous genus. Diplophyllum and Eridophyllum are each restricted to the 

 type species, while the remaining forms are found to fall readily into Synapto- 

 phyllum, Oraspedophyllum, or a Silurian group, possibly the Donacophyllum 

 of Dybowski, and a small Devonian group, probably satellite to that. The 

 unlike structures possessed by some of these genera indicate that their mutual 

 affinities are of not nearer than family rank, so that the expression "diphy- 

 phyllid" is merely one of convenience for the present study. 



Following this paper was ojio on methods of determining the attitnde 

 of strata, delivered 1)y tlie author, and followed b}' remarks by E. B. 

 Branson. 



CRITERIA OF ATTITUDE IN BEDDED DEPOSITS 

 BY LANCASTER D. BURLING 



{Abstract) 



The criteria of attitude may be defined as those evidences by which a field 

 observer may determine which is the bottom and which the top of a given bed, 

 or series of beds, and something as to the history of past changes in the atti- 

 tude of such a section. These criteria are classified and discussed, witli 

 bibliographic references to typical examples. 



The final paper of the pi'ogram was read by E. B. Branson in the 

 absence of the author. 



