36 



ME. J. A. DOUGLAS ON GEOLOGICAL SECTIONS [vol. lxxvi,. 



On the south, however, the Cretaceous limestone continues as. 

 far as Taya Taya, where, capping the prominent escarpment behind 

 the station, it rests with striking unconformity on the older series- 

 (see fig. 4, p. 34). The chocolate-coloured conglomerate of the 

 Saracocha district is no longer represented : the basement-beds here 

 consist of a white and pinkish quartzite-breccia, derived in situ 

 from the underlying rocks. 



In places, small isolated hills, with conspicuously rugged outline, 

 mark the outcrop of the diorite. 



The Devonian beds, which are almost bare of vegetation, are 

 readily accessible by fording the river at Taya Taya, where they 

 are found to consist of olive-green grits and sandstones and black 

 ferruginous shales. Although for the greater part of their extent 

 they appeared to be unfossiliferous, the shales opposite Las Huertas 

 yielded a fairly prolific fauna. 



The lowest beds are here crowded with crinoid-stems and the 

 hollow casts of a bryozoan ; these are succeeded by shales contain- 

 ing abundant brachiopods : — Leptoccelia, Tropidoleptus, Spirifer, 

 Chonetes, etc., usually preserved in the form of casts. The highest 

 beds of the series consist of black shales, with rounded concretionary 

 nodules, which are highly fossiliferous, yielding several species of 

 Conularia, and an occasional trilobite. Although many of the 

 specimens recorded in the accompanying list, owing to their poor 

 state of preservation, are of little value for the purposes of corre- 

 lation or description, an analysis of the collective fauna clearfy 

 shows that these Devonian beds of Taya Taya correspond to the 

 upper part of Steinmann's ' Icla Schiefer ' of Bolivia, characterized 

 by Leptocoelia fl'abellites ; and, from the abundance of the genus 

 Conularia, they may be considered as the equivalent of his 

 ' Conularia -Shales.' 



LiorJiynchus lodenhenderi, Leptocoelia aciitiplicata, and 

 Scapliiocoelia ooliviensis, the forms characteristic of the Devonian 

 beds of Coniri regarded by me as of Lower Devonian .age, appear 

 to be unrepresented in the district now described, and the continua- 

 tion of these beds must be sought still farther west, where they are 

 buried beneath the transgressive Cretaceous rocks. The TaA^a Taya 

 beds, then, probably represent a somewhat higher horizon, and 

 may be correlated with the Marcellus Shales, or lower division of 

 the Middle Devonian Hamilton Group of North America. 



Fattnal List. 



Orthoceras sp. 



Bucaniella aff. dereimsi Knod. 



Platyceras sp. 



Nuculites sp. 



Conularia africana Sharpe. 



Conularia baini Ulrich. 



Conularia quichua Ulrich. 



Conularia acuta A. Rcemer. 



Hyolithes sp. 



Rhynchonella sp. 



Tropidoleptus carinatus Conrad. 



Spirifer aff. mucronatus Conrad. 



Spirifer cf. antarcticus Morris &. 



Sharpe. 

 Spirifer planoconvexus Knod. 

 Chonetes arcei Ulrich. 

 Chonetes aff. coronata Conrad. 

 Orthotetes cf. chemungensis Conrad.. 

 Leptocwlia flabellites Conrad. 

 Dalmanites sp. 

 Phacops cf. rana Green. 

 Phacops aff. schlotheimi Kayser.. 

 Proetus sp. 

 Bryozoa and crinoids. 



