E. T. Newton — GyaptoUtesfroiii Pern. 197 



which he named GraptolUes dentatns ; but finding that they had 

 two branches, united them with Graptoiites (now Bidijmogrnptus) 

 Mnrchisoni ; Grap. foUaceus was likewise included, and as this is 

 a Diplograptid there must be much doubt as to the specific identity 

 of his Bolivian forms, although the published figures leave little 

 doubt as to their belonging to the genus J)ichjmograptas, and 

 consequently point to beds of Llandeilo or Arenig age ; that is, if 

 we are right in using the zonal distribution of Old Woidd Graptoiites 

 as an index for those of Central South America. 



Both Cambrian and Silurian fossils have been described from 

 Northern Argentina (hit. 23^° and 25° S.) by Professor Kayser,^ and 

 from Portezuelo manj' examples of a Didymograptus are noticed 

 which he thinks may be the same form as that brought fi'om 

 Bolivia by D'Orbigny, thus again pointing to Llandeilo or Arenig 

 rocks a long way to the south-east, and confirming the occurrence 

 of strata of that age in the central part of Sonth xlmerica. 



M. J. Balta, in his note on "Fosiles de Carabaya," - mentions the 

 occurrence of graptoiites and annelid burrows at Huayna Tacuma, 

 Santo Domingo, in the province of Carabaya. I am unable to find 

 this locality on any map I have consulted, but Mr. Jessop tells me 

 there is a Santo Domingo a few miles from where his graptoiites 

 were found, and this is probably the place indicated. M. Balta refers 

 his graptoiites to Diplogrnptiis palmeus, Barrande, and D. pristis, His., 

 and he remarks that only Lower Silurian rocks have at present been 

 observed in South America. The genus Diplograptas, however, is not 

 confined to Lower Silurian (Ordovician) deposits, and if the reference 

 of specimens to D. palmeus and B. pristis be correct, then, while the 

 latter points to beds of Bala age or the uppermost part of the 

 Lower Silurian, the former, B. palmeus, indicates Upper Silurian 

 rocks, that is, strata of Llandovery or Tarannon age ; moreover, 

 Salter had already in 1861 recognized Upper Silurian fossils among 

 those brought over by David Forbes. 



The Diplograptus obtained by Mr. Herbert J. Jessop, whether 

 referable to D. truncatus, Lapw., or to a new but closely allied 

 species, may be taken as indicative of beds near the uppermost 

 part of the Lower Silurian. 



So far as we can judge from the evidence of the graptoiites now 

 known to occur in Central South America, there are in that country 

 deposits of Ai'enig or Llandeilo age with the characteristic Bidijmo- 

 graptus Murclnsoni ; beds approximately of Bala age, with Biplo- 

 graptus pristis and Diplograptus near to truncatus ; and possibly strata 

 of Llandovery age, as indicated by D. palmeus. It is to be hoped 

 that before long definite graptolitic evidence of Upper Silurian 

 rocks will be obtained by the discovery of some characteristic 

 Monograptids. 



1 Zeitsch. deiitsch. Geol. Gcsell., vol. xlix (1897), p. 274. 

 - Eev. Cii.'Ui', Lima, vol. i 'ISOS), p. 7. 



