Mineralogy and Petrography. 1109 
of them, including a horn-core and posterior part of the skull 
(Plate XXXII., fig. 8). These fragments were also found in the 
Laramie bed of Montana, probably at no great distance from those 
described by Prof. Marsh. I did not determine the genus to which 
this cranium should be referred, since there were already known nine 
genera of Dinosauria from the same horizon to one or the other of 
which, it was sure to belong. The observations of Prof. Marsh 
will determine this point. The affinity to Hypsirhophus referred 
to by Prof. Marsh indicates Polyonax (Cope) as the form to which 
the species probably belongs, although this is of course a mere sur- 
mise. That genus was described from vertebre and limb and 
dermal bones (Cretaceous Vertebrata U. S. Geol. Survey Terri., 
IlL., p. 63, Plates II. and IIT.). Some of the latter were probably 
identified with doubt as parts of the shafts of limb bones, but they 
resemble more nearly some of the spinous dermal bones ascribed to 
Hypsirhophus by Marsh. 
It would have been well if the final publications of the Hayden 
Survey could have been completed by the Director who succeeded 
im in charge, instead of new publications taken up. In that 
case the continued duplication of the work of the first survey by 
its successor could have been avoided.—E. D. Cope. 
MINERALOGY AND PETROGRAPHY.' 
PrETROGRAPHICAL News.—Liwinson-Lessing? has suggested a 
scheme for the classification of elastic rocks. He would divide 
these into tuffs, breccias, congl tes, pseudoschists and slaty rocks. 
' Tuffs he would confine to rocks made up of crystals, or pieces of 
crystals, and separate minerals, and would subdivide into agglom- 
erates-tuffs (subaéreal) and tuffogenous sediments (submarine). The 
agglomeratic tuffs he would further separate according to structure, 
Tuff-like rocks produced from crystalline rocks by orodynamic 
forces, or by weathering, he would call tuffoids, and distinguish as 
elasto-tuffs and decomposition-tuffs (Verwitterungs tuffen). The 
breccias are composed of pieces of rocks cemented by rock material. 
They are divided into primary, or voleanic, an dary, or 
metasomatic breccias. The volcanic breccias include the lava 
together by a molten rock, and tuff-lavas (Spaltung’s breccia), 
Edited by Dr. W. S. Bayley, sy aged Waterville, Me. 
? Miner. u. Petrog. Mitth., ix., p. 528. 
