328 . ABSTRACTS : TECHNOLOGY 



recovery of nearly perfect individuals forms a distinct contribution to 

 our knowledge of the skeletal anatomy of these extinct turtles. 

 The faunas of the various formations are discussed, following which 

 there is a systematic description of the specimens, including sixteen 

 new species. The illustrations are excellent reproductions from photo- 

 graphs of the turtle shells. R. W. Stone. 



PALEONTOLOGY. — An Eocene flora from Trans-Pecos, Texas. 

 Edward Wilber Berry. U. S. Geol. Survey Prof. Paper 125-A. 

 Pp. 9 (1-9), pis. 3, figs. 2. 1919. 



Six forms of fossil plants, two of them palms, are described. They 

 point to warm temperate climatic conditions with abundant precipi- 

 tation and plentiful ground water. They enable the assignment of a 

 definite age to the beginning of the igneous activity of the region and 

 establish correlations between the floras of the Mississippi embayment 

 and the Rocky Mountain region. It is concluded that the basal tuffs 

 in the Barilla Mountains, in which this flora occurs, are post-Cretaceous 

 and pre- Wilcox in age, and that they and the volcanic activity which 

 they represent were probably contemporaneous with the floras and. 

 similar volcanic activity reflected in Raton and Denver formations and 

 elsewhere in the Rocky Mountain region. R. W. Stone. 



TECHNOLOGY. — The properties of American bond clays and their 

 use in graphite crucibles and glass pots. A. V. Bleininger. Bur. 

 Standards Tech. Paper 144. Pp. 52, pi. i, figs. 23. 1920. 



The properties of American bond clays are described in detail and 

 expressed through characteristic numerical values with special reference 

 to their burning behavior. It is shown that materials equal in quality 

 to those formerly imported from Germany are available and that by 

 suitable blending any desired combination of properties can be readily 

 produced. The characteristics of natural and artificial graphite are 

 described and means suggested for the control of crucible mixtures. 

 The fact is brought out that the main advantage in the use of German 

 glass-pot clay consists in its low fire shrinkage and suggestions are made 

 for obtaining similar conditions with the use of domestic materials 

 and with increased resistance to corrosion. The compositions and the 

 preparation of semi-porcelain and porcelain glass pots are given. The 

 method of casting glass pots as practiced at the Pittsburgh laboratory 

 of the Bureau of Standards is also described. A. V. B. 



