18 GEOIOGICAL MEMOIES. 



As early as 1847 I had recognized the Lias-formation in the 

 Caucasus (by means of fossil plants), but I have delayed to publish 

 anything on the subject until now that Abich's latest work reminds 

 me of it, and gives me occasion to communicate the following remarks. 



In 1845 I received from Herr H. Abich, the well-known explorer 

 of the geology of the Caucasus, various fossils, in appearance corre- 

 sponding to the plants of the Coal-formation, without, as he explicitly 

 remarks in his latest work*, making me acquainted with their 

 geological place. They came from Tquirbul, in the circle Okriba, 

 north of Kutais in Imerethia. The district of Okriba possesses, 

 according to Abich, the interesting conformation of a wide and flat 

 caldron-shaped valley, 20 worsts in diameter, which, on the southern 

 border of the lofty range of the limestone -zone of the Caucasus, 

 totally breaking the continuity of the Chalk-formation, that stretches 

 to the foot of the mountain, is enclosed by it all round ; only the 

 narrow vaUey- cleft of the Eion gives exit to the waters of Okriba 

 to the Imerethian plain. 



The interior of this area is, according to Abich, occupied by a 

 very thick and varied formation of clastic rocks, especially argillaceo- 

 arenaceous laminated marl and clayey sandstones, which contain 

 no organic remains fit for determining the geological age, except- 

 ing some not very abundant carbonized plant-remains. To these 

 shales succeed only a coal-formation, composed of a coal-sand- 

 stone, coarse conglomerate, and coal-beds; the coal, according to 

 Abich's section of the Urgebi Hills, on the Tserdilitsqual, near 

 Tquirbul, having a thickness of 47 Enghsh feet, and being, for the 

 most part, fit for economical purposes. 



I could not refer the fossils collected from these strata to the true 

 Coal-formation. Neither Catamites nor SigiUaria, Btigmaria nor 

 Lycopodiacece, nor other such characteristic plants could be recog- 

 nized; only Cycadaceous remains (fronds of Pterophyllum) appeared 

 in the composition of these coals, bed after bed : and this was the 

 more interesting to me, as I had formerly proved that the old coal- 

 beds are composed each of particular kinds of plants ; and in this 

 case also I saw an example of similar conditions in a younger for- 

 mation. 



Among the plants, the best-preserved, remains belong to a very 

 fine PterojC)hyUum, of the fronds of which the coal appeared to be 

 mainly composed: it stands in systematic order between PL PresU- 

 anmn (Zamia pectinata, Br.) and Pt. taooinum (both from the Oolitic 

 formation of Stonesfield) ; I must regard it, however, as new, and I 

 propose to call it, not Pt Oaucasicwmj as Abich wished, but Pt. Abich- 

 ianum, 



Pt. fronde-pianata, pinnulis integris subpatentibus, lato-linearibus basi asqualibus, 

 approximatis apice oblique rotundatis, 1^-20-nerviis, rhachi latitudine pinnu- 

 larum. 



[With this evidence, Prof. Goeppert considered the coal-beds in 



* Yprgleichende geologische Grundziige der Kaukasischen, Armenisclien und 

 Nordpersischen Gebirge, als Prodomus einer Greologie der Kaukasischen Lander. 

 St. Petersb., 1858, p. 104, &c. 



