61 



Below this shale oceurs a hard calcareous layer less than 

 an inch in thickness. This is especialh^ rich in bryozoans, 

 which sometimes make up the bed. Tl:e shale below this 

 bed is less fossil Ifcrous and fissile than that above. About a 

 dozen sj)ecies of fossils occur, but all of them are rare. 

 Among them is Homnlonotus cleknvi ( Green). 



About four feet below the Trilobite layers is another hard 

 calcareous layer, something over an inch in thickness. This 

 is full of fossils, among which SpirUer granulosus (Conr. ) 

 predominates. It corresponds to the layer noted in a similar 

 position at the upper end of Wannakah Cliff. 



Less than a foot below this calcareous laA'er, or about five 

 feet below the Trilobite beds, appears the first or upper 

 Pleurodictyum bed. The second and third are immediately 

 below it, all of them being exposed in the bed of the stream, 

 beyond the last bend, or not very far from Mr. Avery's barn. 

 None of the beds have a very great thickness, the lowest and 

 thickest not exceeding four inches. As already noted, the 

 little coral Pleurodictyum styloporn ( Eaton ) is wholly re- 

 stricted to them, and occurs in great numbers, being espe- 

 cialK^ common in the middle one of the three beds. With it 

 occurs Spirifer granulosus (Conrad), which is frequently 

 overgrown \\\t\\ bryozoa and corals. 



Altogether these are the richest beds in the lower Hamil- 

 ton shales, holding the relation to the lower portion of 

 these shales which the Demissa bed holds to the upper 

 portion. Their chief interest lies in the presence of 

 Pleurodictytini stylopora (Eaton), which is thus seen to be 

 entirely restricted to the lower portion of the Hamilton 

 shales of this region. The lowest of the three beds is of 

 further interest, as it contains besides the Pleurodictyum, 

 two other fossils, which are not found outside of it.* These 

 are Nautilus magister Hall and Amhocoelia umbonata var. 



*It should be noted, ho^vever, that the second of these. Amhocoelia umbonata 

 var. nana Grabaii, has been noticed in the bed jnst below, the few specimens 

 found, however, diflered considerably from the normal characters of the variety. 



