186 bulletin: museum of comparative zoology. 



developed at these two localities the geographic name Esthonian, 

 which may now with propriety be applied to all the Lower Cambrian 

 strata in the whole district. Of the two localities first mentioned, 

 Kunda, and Strietsberg near Reval, the former presents the better 

 outcrop, and it may be taken as the type-section of the Esthonian. 



Ordovician. 



Packerort formation. Upper part of A2, and A3 (upper part of 

 Ungulitensand and the Dictyonemaschiefer or Alunschiefer),. of 

 Schmidt. (Plate?). 



The most instructive section of the formation to which this new 

 name is given is to be found at the base of the perpendicular 80-foot- 

 high-cliff upon which is built the light-house Packerort at the end of 

 the peninsula north of Baltishport. At the base of the cliff one sees, 

 partly in the water, eight feet of hard, almost white, coarse-grained 

 sandstone, representing the top of the Esthonia formation. Resting 

 upon this is a bed of conglomerate, the^iatrix of which is an iron- 

 stained sandstone, and which contains well-rounded boulders ranging 

 from a few inches up to four feet in the greatest diameter. The 

 boulders are all of sandstone, with some small pebbles of quartz, and 

 are very numerous, making up the whole of that part of the formation 

 which rests upon the Cambrian. This conglomeratic layer is very 

 irregular, and only two or three feet thick. It is succeeded by alter- 

 nations of thin layers of sandstone and a very dark gray, friable, soft 

 shale. Above this comes a very irregular layer, five to ten feet thick, 

 of cross-bedded, coarse-grained sandstone with great numbers of 

 Oholus apoJUnis in the upper part. Then follows a band of thin- 

 bedded dark gray shale like that below, but in certain layers, contain- 

 ing great numbers of graptolites, principally Didyoncma flahcUiforme. 

 As these strata rest upon the undulating surface of the sandstone 

 below they have a variable thickness, from thirteen to eighteen feet. 



The conglomerate at the base of the formation was seen also along 

 the river north of the railroad bridge at Narwa. The pebbles at that 

 locality were all rather small, the largest seen being ten inches in 

 diameter. The interbedding of the shale and sandstone was seen also 

 at Asserien, and although the sandstone and shale of this formation 

 are usually in distinct bands, these sections show that the two are 

 intimately associated and belong to the same time. The conglomerate 

 and sandstone indicate the shore phases of the earliest Ordovician 

 transgression; the shale with the graptolites a later shallow water 



