EOCKS OE BOHEMIA. 611 



on Krejci's map, must run through the heart of Prague for many 

 miles in either direction, being continued past Beroun to the S.W. 

 Moreover the beds of the colony dip N.N.W., i.e. in exactly the 

 opposite direction to the dip of the neighbouring part of the basin. 

 This seems to point to a trough-fault, which is quite in accordance 

 with the nature of the ground around the colony. 



I have seen no traces of the lowest or Diphgraptus-zojie in the 

 colony itself. The Priodon-zone is seen on both sides of the high- 

 road close to the village of Motol, near a conical hiU surmounted 

 by a cross ; it consists of black shales, with limestone nodules and 

 bands, and contains the following Graptolites : — 



Monograptus priodon, Bronn. I Re ti elites Geinitzianus, Barr. 

 vomerinus, Nich. \ 



The Colonus-7.onQ is separated from the Priodon-zone (just as is 

 the case in undoubted beds of e 1 at Vyskocilka) by limestones. 

 The Cohnus-zone yielded Monograptus colonus in abundance. 

 Other fossils than Graptolites occur in the limestones of the colony, 

 among which Dr. Novak has discovered Arethusina KonincMi, pre- 

 served in the Museum at Prague. This is a well-known Trilobite 

 of E in Bohemia, and the genus is not, so far as I am aware, known 

 in any other country. 



The colony at Beranka is a continuation of that at Motol, to the 

 "W. of the latter, and contains the Priodon-zone. 



It has been already mentioned that the fault which would bound 

 these colonies would also pass through the little lenticular mass in 

 Prague, named Colonic Zippe. 



2. Colonie^Ootta. — This is to the S.S.W. of Jinonice, between 

 Prague and Repora, and about two miles to the south of the last- 

 described colonies. It merely exhibits a mass of diabase rising 

 out of alluvial deposits, and including baked sandy shales with 

 Monograptus colo7ius in abundance. It is on the line of strike of 

 the colony about to be described. 



3. Colonie D'Archiac. — Situated about two miles S.W. of the 

 last described. There is no good rock-exposure betwixt the two 

 colonies. I was fortunate enough to examine that under consider- 

 ation, along with Dr. jS'ovak, just after a section had been exposed 

 along a road-cutting, and this showed clearly the relations between 

 the " colony " and the surrounding beds. In M. Barrande's map of 

 this colony (appended to Def. des Col. iv.) a mass of diabase is 

 shown crossing the road to Tfebonice, between the colony and the 

 beds of d 5 to the S.E. of it. This mass does not appear in the 

 road-section, and at this point a clear exposure is exhibited, as shown 

 in the following figure (fig. 7). In this section the beds between X 

 and Y were contorted in every possible manner. A calcareous band 

 containing Monograptus colonus &c. occurred, much folded, near 

 one corner of this mass, and above it were blackish sandj^ shales, 

 similar to those of the top of the colony. Below were black and 

 olive-green shales, with little nodular concretions, like those of d 5, 

 and containing fragments of fossils. The relations of the beds above 



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