EOCKS OF iJOHEMTA. 613 



and below are shown in the larger section across the colony 

 itself (fig. 8). There is no alternative hut to consider the mass 

 between X and Y as filling up the fissure of a fault; for the 

 black Trinudeus-shales, at their southern extremity, are succeeded 

 by the usual green shales and grits of d 5, of which there is no trace 

 here, and the idea of an unconformity is negatived by the smashed 

 nature of the rock. 



This section would also account for the coexistence of the two 

 faunas at one horizon described by M. Barrande (Def. des Col. iv. p. 38) 

 as occurring at the summit of this colony, and before alluded to. As 

 will be seen by the section, there are at least two other faults in 

 connexion with the colony, which are seen in clear exposures. 



The palaeontological evidence of this " colony " is as satisfactory 

 as the phj^sical, the three zones of Graptolites being easily made out. 

 The lowest, or Diplogra^fMS-zone, is bounded by faults on either side, 

 that between it and the shales of d5 being a perfectly clean-cut 

 fracture, whilst the one above, dividing it from the Priodon-zone, is 

 marked by a fissure filled with fault-rubble. The lowest subzone of 

 the Diplograptus-zone is alone to be seen in the roadside cutting. 

 It consists, as usual, of "wafer shales" crowded with Climacograptus 

 scalaris and Rastrites peregrinus. It yielded to a short search : — 



Monograptus Becki, Barr. 

 Rastrites peregrinus, Barr. 

 Diplograptus folium, His. 



Diplograptus tamariscus, Nich, 

 OHmacograptus scalaris, His, 



The Priodon-zone is, as usual, a black flaggy shale, containing bands 

 and nodules of limestone. The included igneous rocks are well de- 

 scribed by M. Barrande in his ' Defense.' The Graptolites obtained 

 were : — 



Monograptus priodon, Bronn. I Monograptus, sp. 



vomerinus, Nich. \ Retiolites Greinitzianus, Barr. 



The Colonus-zone is a sandy black shale, weathering yellowish, 

 and containing limestone bands and nodules. I obtained : — 



Monograptus colonus, Barr. 

 bohemicus, Barr. 



I also obtained Naticella tubicina and Peltocaris ? from a nodule in 

 this zone. 



4. Colony on the road to Vohrada. — This lies between Colonie 

 D'Archiac and the main mass of e 1. Between it and the last de- 

 scribed lie the Trinudeiis-sh.ale8.i and green shales and grits of d 5, 

 whilst between it and the main Silurian mass are green shales and 

 coarse green and yellow grits. It seems to consist of shales included 

 in diabase, and I was unable to find any fossils in it ; but M. Bar- 

 rande (Def. des Col. iv. p. 41) records Monograptus priodon, Bronn, 

 and Uetiolites Geinitzianus, Barr. IN'o section is seen showing its 

 relations to the surrounding beds. 



5. Oohny at Tachlovice.- — The present colony occurs some miles 

 to the W.S.W. of Colonie D'Archiac, in the village of Tachlovice. 

 Its eastern extremity is not seen, owing to overlap of Cretaceous 



