Classification of Sedimentary Rocks. — Grabau. 247 
etc.), or as biorudytes, bioarenytes, or biolutytes. When the 
field relations of the other rocks are determined, they may be 
classed as autoclastics, i.e. autorudytes autoarenytes, or auto- 
lutytes; as atmoclastic, i.e. atmorudytes atmoarenytes or at- 
molutytes, generally of complex composition ; as anemoclastic, 
i.e. anemorarenytes, or anemolultytes, (when pure as ancmo- 
silicarenyte, anemocalcarenyte, etc.) ; or as hydroclastics, i.e. 
hydrorudytes, hydrarenytes, or hydrolutytes, or when pure as 
hvdrosilicirudytes -arenytes, or -lutytes, as hydrocalcirudytes, 
-arenytes, or -lutytes, or as hydrargillutytes, according to com- 
position. Siliceous hydrargillutytes comprise many of our 
Palaeozoic siliceous mud-stones, while most of the typical shales 
of the Palaeozoic, are calcareous hydrargillutytes. The Gene- 
see shale (slate?) of western New York is a siliceous and car- 
bonaceous hydrargillutyte. In all these cases of course the pre- 
fix "hydro" can be omitted, as the rock is understood to be of 
hydroclastic origin. 
The compound terms here given may be found useful in de- 
scriptive writing, especially as they are almost self-explanatory. 
Petrographers may find it desirable in the future, to coin spec- 
ial names for special types under the different groups. Thus 
the anemoclastic calcairenyte (anemocalcarenyte) of the Ber- 
mudas may be called bermudyte, and the name retained for that 
type elsewhere. Or the hydroclastic calcilutytes (hydrocalcilu- 
tytes) of Petoskey may be called petoskeytes, and the name 
restricted to all hydrocalcilutytes which are derived from the 
ground-up mud of ancient coral reefs and deposited in the 
neighborhood of the reef. In like manner the magnesian hy- 
drocalcilutytes of the Beaver islands, lake Michigan, which are 
not directly derived from organic deposits ("zoogenic calc 
rocks), might be called beaverytes, and the name restricted to 
rocks of that origin, texture and composition. Stratigraphers. 
however, will scarcely need terms more precise than those here 
given. 
Palaeontologic and Stratigraphic Laboratory, 
Columbia University, Neiv York. 
