Geology and Paleontology. 639 
necting the mastoid and the frontal, whereas in D. pardiceps Owen 
it only rises 5.5 cm. over the same level. The frontals are less 
developed than in D. leonticeps, the orbits are deeply sunk, and 
the nasal openings are placed far forward, so that it is one of 
the most peculiar representatives of the group. The entire occipi- 
tal region and the bones of the under side are wanting. 
: i strata belong to six genera, viz., 
Diplurus (1 sp.), Ischypterus (18 sp.), Catopterus (5 sp.), Ptycho- 
the English Lias. 
All the species are distinct from any known in the Old World, 
but a species of Ptycholepsis allied to ours is found in the Lias of 
Boll, Wurtemburg, and a species of Dictyopyge has been described 
from the Keuper of Germany. Catopterus seems to be distinct 
from any genus of fossil fishes found in the Old World, but Ischyp- 
terus is very near to Semionotus Ag., which is represented by 
Geo. F. Becker (Bull. Cal. Acad. Sei.) replies to Messrs. Hague 
and Iddings’ criticisms upon his conclusions respecting the pyrox- 
enie rocks of Washoe. The former geologist sees in these rocks 
evidences of two separate eruptions, and therefore divides them 
nto diabase and andesite, while the latter geologists consider both 
