Authors' Catalogue. 331 
similar way are intimately associated with the gabbro and which are 
also, in a measure, allied petrographically and perhaps structurally, 
with the muscovadyte. This whole series, as stated by Gushing, is 
an exceedingly varied one, whether in the Adirondacks or in the Lake 
Superior region. As igneous rocks they shade off toward the gabbro 
and also become very granitic and acid. In their bedded or leaved 
conditions they seem to grade into the Grenville series in the Adiron- 
dacks, and into the muscovadyte series in the region of lake Superior. 
As distinctly igneous rocks they are younger than the associated frag- 
mental (gneisses), and as metamorphosed clastic rocks they are of the 
same age as the Grenville in one place, and as the muscovadyte in the 
other. 
Owing to this great variation in composition and in structure it 
may be dotibted whether any chemical composition can be considered 
typical and characteristic. It is evident that field studies are mainly 
to be depended on to furnish the key to the relations and origin of this 
series of rocks. It is also pleasant to know that Prof. Gushing has 
entered, apparently, upon this branch of inquiry into the geology of 
the Adirondacks with thoroughness and with a just appreciation of 
the value of field study. n. h. w. 
MONTHLY AUTHORS' CATALOGUE 
OF American Geological Literature, 
Arranged Alphabetically.* 
Calvin, Samuel. 
lowan drift. (Bull. Geol. Soc. Am., vol. 10, pp. 107-120, Mch 7 
1899.) 
Case, E. C. 
The development and geological relations of the vertebrates. V. 
Mammalia, continued. (Jour. Geol., vol. 7, pp. 163-187, Feb. -Mch 
1899.) 
Crosby, W. O. 
Geology: south shore [near Boston, Mass.]. (Guide to localities 
illustrating the geology, etc., of the vicinity of Boston, pp. 21-31. 
A. A. A. S., 50th anniversary meeting, Boston, August, 1898.) 
Cushing, H. P. 
Augite-syenite gneiss near Loon lake, New York. (Bull. Geol. 
Soc. Am., vol. 10, pp. 177-192, pis. 19-20, Apr. i, 1899.) 
Daly, R. A. 
A comparative study of etch-figures. The amphiboles and pyrox- 
enes. (Proc. Am. Acad. Arts and Sci., vol. 34, no. 15, pp. 371-429, 
pis. 1-4, Mch. 1899.) 
*Tliis list includes titles of articles received up to the 20th of the preceding 
month, including general geoloKy, physiography, paleontology, petrology and 
mineralogy. 
