OF ARTS AND SCIENCES. 28T 



conditions, appears to have deprived some of them, at any rate, of 

 any capacity for development in the direction of their congeners. 

 The genus Orestias is closely allied to Fundulus, one of the most 

 widely distributed of fresh-water genera. The species of the genus 

 Orestias resemble in a remarkable degree the young of some species 

 of Fundulus, and might be considered, without exaggeration, its em- 

 bryonic type, at a time when the young Fundulus is remarkable for 

 its large head, prominent opercula, its large scales resembling plates 

 along the anterior part of the back and sides. The other genera of 

 fish found in the lakes are eminently fresh-water, having a great 

 geographical distribution. The great number of water-birds recalls 

 to us vividly also the more northern marshy regions, where thousands 

 of ducks and water-hens abound. The mollusca are all species of 

 eminently fresh-water genera, showing nothing very special. The 

 Crustacea, on the other hand, belong mainly to the Orchestiada?, forms 

 which thus far have not been found in fresh water at all : their near- 

 est allies are nearly all marine (see Bull M. C. L., vol. iii. No. 16). 



Although we have from the researches of several geologists, but of 

 Darwin mainly, a pretty good general idea of the immense extent of 

 territory which has been subject to a greater or less elevation along 

 the whole west coast of South America, from the south coast of Ecua- 

 dor to the eastern coast of Patagonia, this elevation appears to have 

 culminated in Central Peru. Yet there has been nothing shown which 

 woTiId lead us to assume such an immense elevation of the land as 

 1 2,000 feet. It is very true that Darwin showed the most positive 

 proof of elevation to a height of about 600 feet ; while terraces, 

 shingle-beaches, and other more or less distinct traces of the former 

 level of the sea, he traced to a height of from 1,300-1,500 feet. I 

 have been able to follow up these traces of elevation somewhat higher, 

 having found at Tilibiche, at a height of 2,900 feet above the level of 

 the sea, corals of genera closely allied to those now found living in 

 the West Indies (see Bull M. C. L., vol. iii. No. 13). These corals 

 were attached to rocks, in crevasses formed between them, much as 

 we would find them attached at the present day in the cracks of rocks. 

 This being near the northern extremity of the nitrate-fields of Peru, 

 throws considerable light on the probability of these deposits having 

 been of marine origin. In fact, the geography of the whole of the 

 Wf St coast of the Andes to the north of Chili seems to point to a 

 former condition of thinofs such as we now find on the west coast of 

 Chili. The plains to the southward of Santiago, bounded by the coast 

 range to the westward, and the Andes to the east, gradually pass to 



