Jurassic of Western Caucasus. 517 



slip over the clays. In the more northern valleys the limestones 

 occur in the bed of the valleys, and are there overlain by a very thick 

 series of clays with gypsum, apparently of Miocene age. Above Psebai 

 the Little Laba cuts through a thick series of sandstone (with plant- 

 remains) underlying the shales and resting upon Triassic limestones. 



The Jurassic succession of the Little Laba valley may be thus 

 tabulated from Rebinder's lists : — 



1 . Oxfordian and Sequanian. — Light brownish grey limestones, very 

 fossiliferous, with an assemblage in which Oxfordian forms predominate, 

 but there is a sprinkling of Lower Sequanian species such as Zeilleria 

 pseudolagenalis, Terebratula Zieteni, and Balanocrinus pentagonalis, 

 Phylloceras, sp. ind., Peltoceras cf. arduennense, d'Orb., Perisphinctes 

 bernensis, Lor., P. consociatus, Buk., P. cf. lucingensis, Favre, 

 P. mazier icus, Buk., P. cf. Michalski, Buk., P. cf. tizianiformis, 

 Choff., P. aff. plicatilis, d'Orb., P. aff. biplex, Dentalium, sp. ind., 

 Ceromya excentrica, Boem.,* Lima Escheri, Moesch, Hinnites velatus, 

 Gf.,* Plicatula, sp. ind., Terebratula Rollieri, Haas, T. of. Zieteni, Lor., 

 Zeilleria pseudolagenalis, Moesch, Waldheimia, sp. ind., Bictyothyris, 

 sp. ind., Rhynchonella lacunosa, Qu..,* Holectypus, sp. ind., Pentaerinus 

 cingulatus, Munst., P. cf . Marcousanus, d'Orb., Balanocrinus pentagonalis, 

 Gf., Miller icrinus cf. icaunensis, Lor., M. Escheri, Lor.,* Serpula, 

 sp. ind., and sponge-fragments. Those marked with an asterisk pass 

 also upward into the Sequanian. 



2. Bathonian and Callovian. — Yellow- grey to rusty-brown sandy 

 limestones, yellow-grey oolitic limestones with geodes of limonite, 

 and sandstones, sometimes argillaceous, with the following: Bathonian 

 forms occurring in the limestones: Jlelemnites atf. canaliculatus, Schl., 

 B. cf. tvilrtembergensis, Opp., B. aff. Jacquoti, Terq. & Jourdy, 

 Pleuromya donacina, Rom., Pseudomonotis, sp. ind., Gervillia, sp. ind., 

 Rhynchonella varians, Sow., var. spathica, Desh., Terebratula aff. 

 sphceroidalis, Sow., T. splicer oidalis, Sow., mut. balinensis, Szajn., 

 T cf. ventricosa, Hartni., Cidaris filograna, Ag. 



In this series the presence of Callovian {Macrocephalus zone) is 

 clearly indicated by the following fossils : Stephanoceras coronatum, 

 Brug., Quenstedticeras, sp. ind., Pecten fibrosus, Sow., Cyclocrinus 

 macrocephalus, Qu. 



3. Bqjocian. — (i) Dark-grey shales with nodules of sphserosiderite 

 (up to 0*20 m. in thickness), which frequently contain ammonites. 

 The following fossils were obtained from this series : Belemnites 

 giganteus, Schloth., B. aff. paxillosus, Q,u., ParJcinsonia Parkinsoni, 

 Sow., Pcecilomorphus aff. macer, Buckra. (ii) Sandstones with plant- 

 remains, overlying Triassic strata. A seam of lignite, 7 inches thick, 

 lias been recorded from these beds, in the Kizilovaya valley near Psebai. 



The entire palgeontological succession is closely parallel to that of 

 Khod near Alagir on the north slope of the Central Caucasus, about 

 80 miles to the south-east. 



Bebinder expresses strong doubts as to the presence of Kimeridgian 

 in the Jurassic of the Little Laba, for in his lists the only species 

 which range so far upwards are Ceromya excentrica, Terebratula cf. 

 Zieteni, and Zeilleria pseudolagenalis, but these are all more characteristic 

 of a lower horizon. Moreover, it would indeed be a matter for surprise 



