Yol. 62.] GRAPTOLITES FROM BOLIVIA. 431 



17. On Graptolites from Bolivia, collected hy Dr. J. W. Evans in 

 1901-1902. By Ethel M. R. Wood, D.Sc. (Communicated 

 by Dr. J. W. Evans, LL.B., F.G.S. Read April 25th, 1906.) 



The graptolites collected by Dr. John W. Evans from Bolivia, and 

 sent to me for inspection, are marked as coming from five separate 

 localities. 



The besc-preserved forms occur in black pyritic shales exposed 

 at c a halting- place on the right bank of the Rio Coranhuata, known 

 as Culi, on the up-stream side of the Puente de Culi (J. 28/4/02).' 

 The rock is cleaved, and the graptolites are in consequence some- 

 what distorted, but the well-known species Bidymograptus hifidus, 

 Hall, is recognizable. Associated with this abundant form there 

 is one small fragment of a slender extensiform Bidymograptus, 

 apparently of the type of B. affinis, Nich., but too fragmentary to 

 admit of specific identification. 



Black shales occurring at another locality ' on the left bank of 

 the Rio Coranhuata, on the down-stream side of the Puente de 

 Culi (U. 28/4/02),' are crowded with graptolites, but unfortunately 

 much distorted and in a poor state of preservation. 



On one slab from this spot several examples of a species of 

 Phyllograptus are recognizable, and one of GlossograpAus. The 

 commonest graptolitic form present, however, is one which it is 

 difficult to assign to any known genus or species. It belongs to 

 the family of the Diplograptidse, and possesses three conspicuous 

 spines at its proximal extremity together with a long virgula 

 distally produced. It is, perhaps, most closely allied to the genus 

 Gryptograptus; but all details as to the form of the thecse are obscure, 

 and the specimens are too distorted to allow of description. 



Another slab from the same locality shows, in addition to this 

 Cryptograptus (?), fragments of what appear to be a Bidymograptus 

 of the ' hifidus '-type. 



Somewhat softer black pyritic shales obtained from ' the left 

 bank of the Rio Coranhuata on the up-stream side of the Puente 

 de Paracorin, and on the down-stream side of the Rio de Paracorin 

 (G. 28/4/02),' show examples of Bidymograptus hifidus, fragments 

 of a Bidymograptus of the ' Nicholsoni '-type, together with an in- 

 determinable species of Biplograptus, 



So far, therefore, as one can judge from the meagre graptolitic 

 evidence available, all these Bolivian black shales occupy approxi- 

 mately the same horizon, corresponding to the upper part of the 

 Arenig formation of Great Britain. The genus Phyllograptus is, so 

 far as known, restricted to the Arenig ; and Bidymograptus hifidus, 

 which has a world-wide distribution, is everywhere characteristic 

 of its highest zone (Lower Llanvirn of Hicks). 



A different type of Bolivian graptolite-bearing rock is met with 

 on the ' hill-slope on the right bank of the Rio de Amantala, on the 

 up-stream side of the Raqui-raqui and the down-stream side of the 

 Rio de Sant' Iago.' It is a laminated shale, extremely soft, and of 

 a pale silky-grey colour, weathering to a dull orange-red tint. It 



2g2 



