TITLES AND ABSTRACTS OF PAPERS 199 



Following Professor Berry^s paper was an interesting account of fossil 

 rock-boring animals, read by the author and discussed by Messrs. Berry, 

 Schuchert, Field, Bassler, and Yaughan. 



GEOLOGIC SIGNIFTGANCE OF F0S8IL ROGK-BORING ANIMALS 

 BY A. L. BAEROWS 



(Abstract) 



Among the marine boring and burrowing animals of the present day there 

 are certain genera of sea-urchins, Echinus and Strongplocentrotus, and pelecy- 

 pod genera., Adula, Lithodomus, Pholadidea, and Parapholas, members of which 

 habitually bore into rock and do not enter less compact materials, liable to 

 crumble or collapse. These may be distinguished from mud and sand bur- 

 rowers and from occasional borers into rod?:, both recent and fossil, by certain 

 morphologic modifications known to be associated with the rock-boring habit, 

 or by characters of the bore itself, showing that it was made in indurated 

 rock rather than in sand or mud. The origin of the boring habit and the 

 method of boring also strengthen confidence placed in the starfish and mytilid 

 borers, and, to a certain extent, in some of the more highly specialized pholad 

 genera as determiners of an indurated condition of the substratum in which 

 they lived, when preserved as fossils in their native holes. The occurrence of 

 fossil nestling shells in the holes of borers is even better evidence of the in- 

 duration of the rock when the borers lived than the presence of the remains 

 of the boring animals themselves. There is evidence to suggest that the ex- 

 posed ledges which these borers and nestlers entered were located in access to 

 fresh ocean water at no very great depth. Borers and nestlers may also be 

 indicative of faults and disconformities, and may constitute the only relics of 

 the previous fauna of the region which they occupied. In the history of 

 deposition in a given locality the full significance of the former existence of 

 an exposed ledge of rock must depend on further information concerning the 

 faunas of the beds in question, the texture of the rock, their stratigraphic 

 relations and correlations with other beds, and the recurrence of similar con- 

 ditions in these respects over a wide range of territory. 



The following paper on new genera of Paleozoic corals was then given 

 and illustrated by sketches. Discussed by G. H. Chadwick, with reply 

 by the author. 



NEW GENERA OF CORALS OF THE FAMILY OF GTATHOPRTLLIDJE 

 BY AMADETJS W. GRABAU 



(Abstract) 



The genera discussed were Pinnatophyllum, StereopJiyllum, Merophyllum, 

 and Blothromissum, among the simple GyathophytlidcB, and Pristiphyllum and 

 Calvinastrwa among the compound ones. The structure, genetic relations, 

 distribution, and migration were considered. 



XIV— Bull. Geol. Soc. Am., Vol. 28, 191G 



