Heview of Recent GeologicaJ Liteiuifure. 321 
liorseback aad at the eutrauce even bj- wa^oa, and it is possible to ride 
to the falls in the contact zone. The outlying theralite buttes can all be 
visited by wagon." 
'■'•Geologie de I'ancienne Colomhie, BoUvarienne, Venezuela, Nouvelle 
Grenudd et Ecuador" par Herman Kakstex, Berlin, E. Friedlander & 
Son. 
We distinguish in the region studied (Columbia, Venezuela and 
Ecuador) live definite geological periods of which the Jurassic is the 
oldest and has only recently been recognized in a locality in Columbia. 
The next period, however, the Lower Cretaceous outcrops in the moun- 
tains of the whole region and is characterized by a great variety of 
cepholapods. The presence in the lower strata which are speoiallj' 
marly, of Belemnites, Ptychoceras humboldtianus Krst., Ammonites 
nieggerathii Ki-st., Am. rothii Krst., Am. sawtapcinus d'Orb., Am. bous- 
singaultii d'Orb., Hamites arboleda- Krst., might perhaps justify two 
subdivisions of this period. 
The third series, the Upper Cretaceous, characterized by large deposits 
of limestones, sandstones and siliceous beds, may be recognized paleon- 
tologicallj^ by a great quantity of Kudistes which appear toward the 
•east, and the Polj^thalamias, ainmdant in the centre and in the west. 
The fourth period, the Tertiary, is cliaracterized by the abundance of 
vertebrate remains and the presence of pebbles and thick conglomerates 
formed at the expense of the siliceux beds of the older periods. Also 
by the great extension of micaceous marls, traclu^tic cinders and lupilli. 
The fifth period, the (Quaternary, is represented by washings, gravels, 
beds of pebbles, and breccias witli shells on the sea coast; the shells be- 
long to species living at the present time. 
Several cases of unconformity in the respective disposition of these 
five series, show that they also correspond to distinct epochs of eleva- 
tion, and the geographical distribution of the Quaternary proves, in the 
most convincing way, even in the absence of a clear unconformity with 
the Tertiary, that these two periods wei-e eles'ated at different times. 
The imconformities observed in the neighborhood of San Pablo in the 
lower Magdalena river probably mark this historical break. 
The (Quaternary has slight extension, some portions of tlie coast, 
somewhat elevated, belong to it. The Tertiary period is more developed; 
almost the whole of tlie immense plains of the Orinoco and dou1)11ess 
lai'ge part of those of the Amazonas, belong to it; the highest summits 
of the actual continent, date from this time also. 
The Cretaceous, in which investigations show several distinct epochs, 
formed elongated islands in the Tei'tiar\" sea, in lines toward the north- 
•east. The eastern island was the present massive of Cumaria; another 
island of the eastern series represented the massive of ^Irrida, and the 
western island, surrounded to the south b^^ an arclilpelago of small vol- 
canic islands, was traversed bj- mountain chains, ricli in veins, bearing 
gold and platinum. 
It is ([uite remarkal)k' that the steeper sloi)es of the Cretaceous re- 
