part 3] TiiEOUCiH the andes of perf AjN^d Bolivia. 283 



Plate XVJI. 



Fig. 1. Sc/iZcenbac/i m cf. beU-aapi (Marcou) Bose. Albian. Saco. near Oroya, 

 Peril. (Natural size ; see p. 269.) Portion of a cast of a large 

 indiyidual. 



2. Schloenhachia sp. Albian. Saco, near Oroya, Peru. (Natural size ; 



see p. 270.) Probably a young example of 8chl. hellxnapi. 



3. Schlcenhachia sp. (cf. Schl. chihualiuensis Bose). Albian. Yauli, 



Peru. (Natural size ; see p. 269.) 



4. Schloenhachia ventanillensis (Gabb). Albian. Saco, near Oroya, 



Peru. (Natural size ; see p. 270.) Specimen showing adult type of 

 ornamentation. 



Plate XVIII. 



View of the upper part of the Morococha Valley, showing the Anticona 

 laccolite and Lake Huacracocha. (See p. 261.) 



Plate XIX. 



Upper part of the Anticona laccolite, showing dacite capped by Cretaceous 

 limestone. (See p. 261.) 



Plate XX. 



Geological section through the Andes from Callao to the Perene River. Scales : 

 horizontal, 1 : 400,000 ; vertical, 1 : 100,000. For ' Oyora,' read 'Oroya.' 



Discussiox. 



Dr. J. W. Eyans said that the paper was a valuable contribu- 

 tion to our knowledge of the geology of Peru. The comparison 

 between the geology of this section across the Andes with those 

 previously described was full of interest. He suggested that the 

 change of strike from roughly north-west towards north- north- w^est 

 was not without significance. Ultimately, still farther north, the 

 strike became north and south. In a paper on the rocks of the 

 Madeira Falls the speaker had contended that the lines of folding 

 in South America with a north-west and south-east direction w^re 

 older than those striking north and south, and this view was con- 

 sistent Avitli the facts adduced by the Author of the paper just 

 read. 



Prof. W. J. SoLLAS complimented the Author on a brilliant 

 termination to his long-continued labours. The end worthily 

 crowned the work. It was pleasing to contrast the circumstances 

 in which the Author, in polished and easily-flowing language, had 

 so lucidly expounded his results, surrounded with friends and all 

 the comforts of civilization, with the laborious, often painful, and 

 sometimes perilous adventures which had attended his wanderings 

 among the desert plains and high mountains. 



The Aulhor had wisely abstained from entering upon hypothesis, 

 but it would be interesting if he could let his auditors see a little 

 deeper into his mind, and inform them as to what he thought about 

 the mechanism of mountain-building. In such a lofty range one 

 might well have expected mighty overthrusts, some plains of ' Pied- 

 mont ' overriding the ' high Alps,' but we were told of nothing 



