598 J. E. MARE, ON THE PKEDEVONIAN 



shale. The lianestones are easily distinguished from any of those 

 before described by their compact texture and strongly nodular 

 character. 



G g 1. A dark grey, compact nodular limestone, mottled with 

 irregular black spots in places ; the nodules are three or four inches 

 in their longer diameters, which are parallel to the bedding. Inter- 

 stratified black shale beds, a few inches thick, occur rarely. Chert 

 nodules are irregularly distributed in the limestone. At Hlubocep 

 a siliceous bed occurs at the top. Fossils are sparsely distributed. 



G g2. A compact, unctuous, mottled shale of no great thick- 

 ness, with nodules and bands of grey limestone with black mark- 

 ings. The shale is usually of an olive-grey, leaden grey, green, or 

 reddish colour. 



G g 3 strongly resembles g 1 in lithological character, but is 

 usually of a lighter colour, often stained pink, otherwise weathering 

 to a buif- colour. The fauna, however, is very different, being cha- 

 racterized by the numerous genera of Cephalopoda which it contains. 



Etage H consists of grits and shales : there is a total absence of 

 any calcareous rock. It is divided into three bands of no great 

 thickness. 



H h 1. Grey non-micaceous shales, ripple-marked, and crowded 

 with fucoid remains. It is well exposed at Hlubocep, Hostin, &c. 



H h 2 resembles H h 1 in lithological character, but contains 

 interstratified grit bands. 



H h 3 is lithologically similar to H h 1. 



§ 3. The Associated laNEOus Eocks. 



The igneous rocks of the Predevonian basin of Bohemia are many 

 of them, at present, the subject of study of the eminent petrologist 

 Boricky. The following is a list of the principal ones which I 

 noticed : — Granite, Quartz Felsite, Mica-trap, Porphyrite, Diabase, 

 Diorite, Eclogite. 



Granite. — This rock seems to be confined to the older Pre- 

 cambrian series. I have examined it in the neighbourhood of 

 Mnichovice to the south of Prague. It is here very hornblendic. 

 Near Klokocna, north of Mnichovice, a porphyritic granite is seen, 

 with large white crystals of orthoclase. 



To the south of Pribram, granite is seen in the neighbourhood of 

 Milin, along the boundary between the older and newer Pre- 

 cambrian series. It, however, seems to be faulted against the 

 newer series, as this is not much altered near the boundary with 

 the granite. The granite is certainly Precambrian, for the base- 

 ment conglomerates of the Cambrian system are largely made up of 

 granitic materials. 



Quartz Felsite occurs in dykes intruded in the Precambrian and 

 Cambrian rocks in many localities. The dykes appear to be of 

 normal character, and of no great interest. 



Mica-hmp. In the neighbourhood of Strasnice and Weu Strasnice, 

 a few miles east of Prague, several mica-trap dykes cut through the 

 shales of d 5. The dykes in every way resemble those occurring in 



