﻿6G 



PROCEEDINGS OE THE GEOLOGICAL SOCIETY. 



[Nov. 21, 



pear from Mr. Forbes's statements, that it could only be from the 

 sandstones at their very base ; and I must claim these as Upper 

 Devonian. 



Favosites (?), sp. PI. IV. fig. 10. 



I find no pores in any of the tubes (but only some tubercles), and 

 very few traces of tabulas. Possibly it is not of this genus. 



Locality. Given to Mr. Porbes (by Mr. Bogen, of Tacna) as having 

 been found near Oruro. 



UPPER SILURIAN. 



All the thick beds of sandstone, intercalated with many layers of 

 sandy shale, appear to lie in the upper part, or middle part at least, of 

 Mr. Forbes's Silurian section ; and in these the chief part of his fossils 

 were found. The lower beds (chiefly shale and thin sandstones) 

 contain the Bilobites (or Cruziana) and very little else ; and, seeing 

 that his sections gave a measured thickness of at least 15,000 feet 

 (all of which, as he judges by the mineral aspect, belongs to one and 

 the same series), there is much reason for supposing the lower part 

 to be of Lower Silurian date. This is borne out by the presence of 

 the Bilobites, which, as above noted, is chiefly a Lower Silurian type. 



D'Orbigny has figured a Graptolite, with one row of cells, from 

 South America ; and this alone would prove the presence of Silurian 

 rocks, upper or lower. It is from Tacopaya, Santa Cruz. 



Homalonotes Linares, n. sp. PI. V. figs. 1 & 2. 



Body (?) faintly trilobed (fig. 1 «) ; pygidium (fig. 1 b) li inch long, 

 and about as broad, triangular, regularly convex, with the sides not 

 abruptly bent down. The axis is but faintly marked, quite as broad 

 as the sides, and scored by about sixteen rings ; the sides show 

 nearly as many furrows, none of which reach the margin. The apex 

 is pointed, the tail gradually tapering to it, not abruptly acuminate. 

 The sides (apparently from fig. 16) are bent inwards beneath; and 

 the apex also shows some indications of a broadish triangular space. 

 The whole surface appears smooth. 



The species is not unlike H. deVphmoc&phaMs } Murch., but has 

 many more ribs, and a longer axis. 



Locality. Prom the highest point reached by its discoverer: he 

 found it on the all but inaccessible face of Mount Illampu, at the 

 height of 20,000 feet. Named in honour of his Excellency the 

 President of Bolivia. 



HoMALOXOTES, sp. PI. V. fig. 3. 



Not perfect enough to describe. It has a blunt rounded shape, 

 like that of H. obtusus, Sandberger, and several other German and 

 Prench species from Devonian rocks. The axis is more strongly 

 ribbed than the sides, and the surface is roughly granular. 



Locality. From the same mountain as above, at a somewhat lower 

 level (about 15,000 feet). 



