12 BULLETIN 77, UNITED STATES NATIONAL MUSEUM. 



sandstone passes into the Glauconite limestone. The Glauconite 

 sandstone is apparently the record of a transgressing sea and its 

 several parts may therefore be of different ages. No bryozoans have 

 been found in division A3. Likewise none has been recorded from 

 division Bl, although it is probable that some of the bryozoans listed 

 as occurring in B2 will also be found in the upper part of Bl. 



B2. Glauconite limestone.— The presence of scattered glauconite 

 grains gives this limestone a light green tinge, although in places it is 

 of a reddish color with scattered greenish spots. The lowest beds are 

 sandy and are marked by the trilobite Megalaspis planilimbata 

 Angelin. The upper beds contain less glauconite and more shale. 

 Tliroughout gastropods are wanting and cephalopods are rare, but 

 trilobites, brachiopods, and bryozoans are not uncommon. Orthis 

 parva Pander, Poramhonites reticulatus, P. alius, P. parvus, and 

 Clitambonites plana of the same author are the predominating brach- 

 iopods, while Dittopora clavseformis Dybowski, D. annulata Eichwald, 

 Stictoporella gracilis (Eichwald), Dianulites fastigiatus Eichwald, D. 

 petropolitanus Dybowski, and Diplotrypa hicornis Eichwald, are the 

 most abundant of the described bryozoans. 



Among the trilobites the genus Asaplius is well represented, and 

 species of Pterygometopus, CJieirurus, Lichas, and Ampyx are present. 

 The peculiar BoTboporites and the cystid genera Glyptocystites and 

 Ecliinoencrinites make their first appearance here. 



A local movement at the end of this division gave rise to slight 

 erosion and to the formation in Esthonia of a thin zone of phosphatic 

 concretions known to the Russian geologist as the "Untere Linsen- 

 schichten." West of Reval this band is absent and the Glauconite 

 limestone is followed by a sandstone phase of the overlying Orthoceras 

 limestone. The time break here is slight since the change in fauna is 

 not great. 



In his studies Lamansky has recognized three subdivisions in B2 in 

 the government of St. Petersburg, and has described and listed their 

 faunas. The lowest subdivision (B2a) is composed of rather compact, 

 brightly colored limestone layers, rich in glauconite, and 5 to 10 

 inches thick. This zone, which altogether is only about 6 feet thick, 

 is known as the '' horizon with Megalaspis planilimbata, M. limbata, 

 and Asaplius priscus," and contains a fauna of which brachiopods 

 related to those of the underlying division Bib form a considerable 

 part. The strata of subdivision B2b are less compact, thinner lime- 

 stone layers with some shale, also amounting to about 6 feet in thi 3k- 

 ness. Glauconite is less abundant in this zone, which receives its 

 designation from the characteristic trilobites Asaplius hrbggeri and 

 OncTiometopus voTborthi. 



Subdivision B2c, the ''horizon with Asaplius lepidurus and Mega- 

 laspis gibbus," is a gray, rather compact limestone 8 to 10 feet thick, 



