Wm. F. Prouty — Meso-Silurian Deposits of Maryland. 573 



Above the preceding there is a zone two feet in thickness in 

 which occur great numbers of Camarotoechia obtusiplicala 

 mingled with C. sp. nov. and Cuneamra sp. nov. 



The uppermost 50 feet of the Meso-Silurian rocks are in 

 general largely shale and sandstone. They contain very abun- 

 dant Ostracods and poorly-preserved Bryozoa and, in addition, 

 so far as studied, only two fossils : 

 Homeospira evax var. nov. 

 Ctenodonta sp. nov. 



Table Showing Number, General Relation and Affinities of 

 Maryland Meso-Silurian Fossils. 

 Number of forms studied : 



Number of species and varieties studied 56 



Number of species previously described 32 



Number of new species 20 



Number of new varieties 4 



Percentage of new forms 



Percentage of new species __ 35*7 



Percentage of new varieties _. 7*1 



Percentage of new species and new varieties 42*8 



Occurrence elsewhere : 



Number of species occurring in Arisaig 10 



" " " English Silurian 8 



" " " Anticosti 5 



" " " Ohio Clinton... 1 



" " " " Niagara 15 



" " " Indiana " 16 



" " " " Clinton 1 



" " " New York Rochester. 12 



" " " New York Lockport.. 3 



" " " Rochester and Lockport 2 



" " " Niagara and not refer- 



red to either Rochester or Lockport 3 



One-fourth (8) of all the previously described species occur 

 in the European deposits, of which species seven are also found 

 in the middle United States. 



Number of different species cited from either Anti- 

 costi, Arisaig or English deposits ._ ._. 18 



Number of these cited from either Indiana or Ohio 12 



From a study of the foregoing fossil lists and the above 

 table one is impressed with the marked faunal difference 

 between the Meso-Silurian deposits of Maryland and those of 

 Western New York and the interior. The fact that there are 

 so many new species (42 per cent of all studied) argues very 

 strongly in favor of the supposition that the Maryland Meso- 

 Silurian deposits were laid down in a sea distinct from that of 

 "Western New York and the interior. This argument is fur- 

 ther strengthened by the fact that several of the most promi- 

 nent species of the interior Meso-Silurian sea are not repre- 



