1062 The American Naturalist. [November, 
Yojoa, whilst on the western portion of this country the mountain- 
ranges extend nearly from east to west, as is the case with the montanas 
de Jutegalpa, and the montanas de Tonpocente. 
We have thus in Honduras two main directions of mountain extent, 
—north to south, and east to west,—with a great series of other ranges, 
which intersect the above directions at various angles. 
The zone of extension of these ranges is usually not in form of 
straight lines, but bent or curved, passing even into a circle, in which 
case the whole range, with its enclosed surface or valley, assumes a 
huge crater-form. A similar effect is sometimes obtained by the 
accumulation of mountain or mineral masses of a different lithological 
character in a peripheric zone, around an undisturbed centre. 
Most of the ranges which present this curved zone of accumulation 
are but sections of large circles, or waves of undulation, in the 
center or height of which the protrusion of fused masses occurred. 
The topographical structure of Honduras, with its diffused arrange- 
ments of mountain ranges of different eruption centers, is therefore 
most favorable for a display of numerous valleys, which are formed at 
the expense of large plateaux. 
In regard to the shape and origin of the valleys of Honduras, we 
may make the following classification. Valleys are formed: 
1. By the folding up of upheaved, undulating mountain masses. 
2. By the accumulation of eruptive masses around an undisturbed 
center. 
3. By the erosive action of water. 
The first class of valleys is not often found in Honduras; they 
principally occur toward the Atlantic or plutonic coast. 
The second class is of most frequent occurrence, usually of volcanic 
origin. Their manner of formation has been already explained by the 
deposit of fused mineral masses, around a centre which is the actual 
base of the valley. 
The common form of valleys of this class is a round or elongated 
one, but various other shapes occur, as, for example, oblong ones, as 
the result of the intersection of two parallel mountain ranges. In fact, 
it would be impossible for me here to describe the diversified aspects 
of this class of valleys, originated as already explained, but subjected 
to manifold alterations by previously-existing objects. 
I proceed to another group of numerous valleys, which I may call 
crater-valleys, as they are nothing but craters or vents of volcanic 
ranges now inactive. Their ordinary form is circular, and the base of 
the valleys is from two to ten miles in diameter. Usually they occur 
