Review of Recent. Geological Literature. 185 
Colima, by Sr. Ezequiel Ordoaez, and in the states of Pueblo and Tlax- 
cala, by Sr. Jose G. Aguilera. Then come about twenty pages of alti- 
tudes in various parts of Mexico, mostly of moderate amount, up to 
2000 feet, on the plateaus, and not containing any of the mountain 
peaks. This concludes the first part of the volume. 
The second part, which will be of more interest to geologists general- 
ly, commences with a summary of the geology of Mexico, by Sr. Jose 
G. Aguilera. Beginning with a short geographical account of the 
country, he proceeds to a more minute geological description. 
"Geologically considered, Mexico is comjjosed of three parts. The 
first, the more ancient and least extensive, consists of a great mass of 
granite, gneiss and schist, which occupies most of the south of the 
country, and reaches from the Pacific to the eastern coast." 
"The second containing deposits dating from Palaaozoic time to our own 
day is found in the northern, southern, eastern and central parts of the 
country; and the third, almost of equal size and importance, is princi- 
pally composed of eruptive rocks of modern date." 
"The arch«an rocks of Mexico are numerous, varied and consist 
among others, of a porphyritic gneiss like an 'augengneiss'— gueissic phyl- 
lades, passing into the former and mica-slates conformable to the fore- 
going." 
The existence of Silurian strata is evidently doubted. Sr. Aguilera 
says: "There are in our collection a few specimens of slate containing 
good individuals of Orthis testudinaria Dalman, a Trenton species. 
This was sent to Dr. Ant. del Castillo and bears the label 'Estado de 
Guerrero.' But the late director went several times to the locality to 
verify the statement, and could find no ti'ace of any fossil in any rocks 
likely to have yielded it." 
The Devonian system is apparently in the same state. A Devonian 
goniatite, said to come from Apulco, has in like manner called out sev- 
eral journeys to the place, but all to no purpose. 
The existence of Carboniferous strata is, however, proved by the oc- 
currence of Productiis semireticulatus. But certain beds which had 
been referred to the Upper Carboniferous by Frazer, Heilprin and Hall 
have now, on more and better evidence, been placed in the Cretaceous 
system, as they hold Lima, Ariomia, Scaphites, etc. 
The Carboniferous of Mexico has thus far proven very barren ; a mea- 
gre list of four species is preserved and only two of them specifically 
identifiable, composing its whole known fauna. 
The different formations composing the Mesozoic system are not all 
represented in Mexico, those which are found being the upper part of 
the Triassic and Jurassic and almost all of the Cretaceous. The rocks 
of the Triassic are quartzose sandstones and hard shales varying in 
composition both vertically and horizontally. In consequence of strong 
and long continued erosion the rocks of this system have very largely 
disappeared, and a number of small patches are all that remains to tes- 
tify to their extent when formed. The fossils are plants and were 
studied by the late Prof. Newberry, whose names, with few additions, 
