Explanatory note to the maps. 
The topographical map was worked out during the wintermonths 
1915 by the topographer of the Direction of Mines, Buenos Aires, 
mr Jorge Schultz contemporarily with my own field works. 
The original field sheets in greater scale were reduced to the scale 
1:100,000 and connected to form a map of the whole Sierra de 
Umango area, except the western and northern parts of the Cerro 
Cacho complex, which remained unmapped. The present map 
shows also nothing of the mountains more to the west, i. e. the 
very border of the Cordillera, which the Sierra de Umango com- 
plex joins (Pampa de Leoncito and surroundings). Neither the wes- 
tern side of the Guandacol valley — the Precordillera Riojana — 
nor the eastern wall of the Vinchina valley — the Nevado de Fa- 
matina — are shown on the map. These mountains have, however, 
been mapped in other connections. To get a better orientation of 
the main topographic features in this part of the Republic a map 
of smaller scale should be” used. The best existing is the hypso- 
metric map of Ludw. Brackejbusch (1893). 
The geological map reproduced on the cover-sheet was pre- 
pared after the field work were finished and as soon as the topo- 
graphical sheet was to the writers disposal. Thence only the main 
geological features were fixed, partly because the scale of the map 
is reduced to a considerable degree. I believe, however, that the 
quite numerous figures in the texte may be a kind of une ee 
‚to the geological picture of the area in question. 
