Lozi'cr Silurian of Wisconsin and Minnesota. 323 



Q. tricenaria Con., are known to occur, Stictopora mntabilis Ulr., 

 thoiig-h perhaps not confined to these strata, yet occurs in such 

 numbers here that the name Stictopora seemed appropriate in 

 designating this bed. 



The next twenty feet is the Fucoid bed. The shale is made 

 up largely of fucoidal masses and of calcareous laminae some- 

 what irregularly distributed. 



At Saint Paul there is, first, 15 feet of shale; then 5 in. lime- 

 stone; 18 in. shale; 3 ft. of hard crystalline strata that weather 

 reddish brown. This bed will be recognized at once in Ramsey, 

 Dakota and Goodhue counties, by the quantity of fucoidal re- 

 mains or by the occurrence of Phylloporina corticosa Ulr. In 

 Fillmore county I have found the evidences of this bed but never 

 the bed itself exposed. Orthis pectinella Con. occurs for the first 

 time at this horizon and also Rhynchonella increhescens Hall. 



The strata that lie upon the Fucoid bed are without fucoidal 

 remains but are much more fossiliferous upon the whole. Zygos- 

 pira recurvirostris Hall^ Rhynchonella increhescens Hall, are ex- 

 tremely abundant. This bed is characterized by the absence of 

 certain species that occur above or below. The name Zygospira 

 bed is proposed from the most numerous species. There is in this 

 bed three feet of hard shale, four feet of ordinary shale, and one 

 foot of shaly limestone — eight feet in all. 



At the upper limit of the Zygospira bed a new fauna appears. 

 Receptacnlites, Flatystrophia, Orthisina — which are unknown be- 

 low. Orthisina [Hemipronites] americana Whitf., has not been 

 found except in this bed and hence the name Orthisina is pro- 

 posed. 



Lithologically the Zygospira and Orthisina beds are difficult 

 to distinguish, and later searching may succeed in merging the 

 former into the latter. In both, there are peculiar calcareous 

 lumps, irregular in shape, rounded in the latter bed and of lighter 

 color than the other parts of the shale, and alternating in strata, 

 with thin smooth surfaced limestone layers. At Saint Paul only 

 part of the Orthisina bed remains. At Kenyon, Goodhue county, 

 there is over fifteen feet of this bed exposed. In Olmsted and Fill- 

 more counties the exposures of this bed are rare, and these do not 

 show more than ten feet thickness. In the last named county the 

 bed consists rather of shaly limestone than a shale. 



Just where the division between the Trenton and Galena 

 should be drawn so as to agree with the division in Wisconsin is 



