190 BI'LLETIX: MVSEUM OF COMPARATIVE ZOOLOGY. 



of green and gray limestone and pieces of shale; and at Catherine 

 Park, Reval, the green "Glauconitkalk" is likewise followed by a six 

 inch layer of conglomerate in which there are pebbles of limestone 

 full of glanconite. This unconformity is not newly discovered, but 

 was distinctly foreshadowed in Schmidt's papers, and was definitely 

 worked out by Lamansky, who, howe^"er, placed the layers containing 

 Asaphiis expansus in the overlying formation instead of with the older 

 strata, as the evidence seems to require. (Plate 2). 



The doubtful member of this formation is the green sand. It is 

 placed here, because there is an undoubted break in the sedimentary 

 record between the Dictyonema shale and the M. planilimbafa lime- 

 stone. In Norway and Sweden one finds between these two forma- 

 tions the Ceratopyge limestone, with a fauna which, though it occupies 

 no great thickness of strata in Scandinavia, really endured for a very 

 long period of time. During this interval no deposition was taking 

 place in the region in Russia here discussed, and, apparently, neither 

 was there any great erosion, the district standing nearly at sea-level. 

 During some part of this time the green sand seems to have accumu- 

 lated, perhaps as a beach sand, at least at first, but probably reworked 

 as a whole or in part by the inAasion of the sea in which were deposited 

 the Walchow sediments. It differs from an ordinary beach' sand not 

 only in its green color, but in the presence of much fine clay. It 

 usually shows neither stratification nor cross-bedding. The fauna is a 

 scant}^ one. In the west, on the Baltishport peninsula and near 

 Reval, a few specimens of Oholus liugulacformis Mickwitz, a Lingula, 

 a Siphonotreta and conodonts have been found. At Papowka, 

 Lamansky has referred to the " Glaukonitsand " a sandy part of the 

 limestone, and has obtained from it a considerable fauna which he 

 considers to be distinct from the regular M. planilimhata fauna and 

 allied to the Ceratopyge fauna of Scandinavia. This fauna is how- 

 ever, too closely allied to the M. planilimhata fauna to ihdicate the 

 presence of either a Ceratopyge or Lower Didymograptus fauna, and 

 the strata containing it would seem to go naturally with the limestone 

 rather than with the sandstone of the section. 



So far as I have seen it, the fauna of the green sand seems to be 

 allied with that of the L'ngulite sandstone below, rather than with the 

 limestone above. The sand and clay content of the bed may easily 

 have been derived from the denudation of the underlying Packerort 

 formation, which was undoubtedly uplifted and subjected to erosion 

 at some localities, even though we can not now point definitely to the 

 particular places, and, such being the case, it seems more probable 

 that the sand belongs to the later and not the earlier sedimentation. 



