TITLES AND ABSTRACTS OF PAPERS 203 



AGE OF THE AMERICAN MORRISON AND EAST AFRICAN TENDAGURU 



FORMATIONS 



BY CHAKLES SCHUCHEET 



{Abstract) 



Tlie very interesting dinosaur-bearing Morrison formation is underlain by 

 the Sundance and overlain by the equivalent of the Washita. The latter is 

 the last series of the Oomanchian, though some European stratigraphers regard 

 it as of early Upper Cretaceous time. On the other hand, the Sundance is 

 regarded by some paleontologists as of early Upper Jurassic age and by others 

 as late Upper Jurassic; the evidence of the ammonites and sauriaus appears 

 to indicate the Kimmeridgian rather than the Oxfordian. Between the Sun- 

 dance and the Morrison, it is now widely held, there is a time break and the 

 two series of deposits overlap from opposite directions. It appears that during 

 this interval there occurred the Sierra Nevada orogeny, and accordingly, on 

 the basis of diastrophism, the Morrison should be of Oomanchian age. The 

 floral and faunal evidence of the Morrison is also rather in harmony with this 

 conclusion, and is further supported by that of the East African Tendaguru 

 series, which has Jurassic and Lower Oretaceous marine and dinosaur faunas. 

 This conclusion also falls in line with the decision of the Committee on 

 Geological Names of the United States Geological Survey, who early in 1916 

 deemed the evidence sufficient to warrant the classification of the Morrison as 

 of Lower Oretaceous age. 



The excellent results obtained by special methods of study were de- 

 scribed in the next paper, which was illustrated by photographs and a 

 stereoscope. Discussed by A. P. Foerste. 



EXTERNAL STRUCTURE OF STEGANOBLASTUS AS REVEALED THROUGH GUM 

 MOUNTINGS AND PHOTOMICROGRAPHIC STEREOGRAMS 



BY GEORGE H. HUDSON 



{Abstract) 



The writer has made a complete analysis of the surface with all sutures 

 clearly revealed. It has large deltoids, sagittate, with a small group of plates 

 in the sinus. The distal extensions of the deltoids pass into the sinus of the 

 radials by a diagonal and adjustable sliding suture, as in Pentremites only 

 the deltoids reach nearer the arm tip. The deep groovings on the plate sur- 

 faces were for branching epispires, which were protected by a forest of spines. 

 The floor and cover plates rested directly against the deltoid, and under these 

 was a double sublancet plate. The "pore plates" had no pores, but were 

 covered with spines. 



A second study by the same author, in which the same methods of 

 research were employed, was then presented. 



