214 



JV. H. Darton — Upper Silurian rocks of 



found, and in the greatest abundance. They all consist of 

 casts or impressions and are preserved to perfection in a soft 

 white or buff matrix of very fine grain and uniform texture. 

 Their abundance is wonderful, and nearly all the individuals 

 noted in the following table were found in half a cubic meter 

 of shale. (Excavation is now necessary to expose this bed.) 



It was considered desirable to ascertain the relative propor- 

 tions of each of the species represented, and a count was kept 

 until 500 individuals had been recognized, with the results 

 given in the first column after the name; those noted in the 

 second column were obtained at other times. 



1 



2. 



2 



1. 



3 



1. 



4 



3 



5 



1. 



6 



2. 



7 



1. 



8 



1. 



9 



3. 



10 



3. 



11 



1. 



12 



2. 



13 



3. 



14 



1. 



15 



2. 



16 



1. 



17 



2. 



18 



2. 



19 



2. 



20 



2. 



21 



2. 



22 



2. 



23 



2. 



24 



3. 



25 



3. 



26 



3. 



27 



3. 



28 



1. 



29 



2. 



30 



1. 



31 



2. 



32 



3. 



33 



2. 



34 



2. 



35 



2. 



36 



3. 



37 



2. 



38 



3. 



39 



3. 



Astylospongia inornata H. 



Fenestella. Three forms 



Several undetermined Bryozoans 



Cladopora seriata H 



Crinoids, many fragments 



Tentaculites elongatus H. 



Discina discus H.I 



Discina Conradi H. _. 



Pholidops, two species, undetermined... 



Orthis oblata H. 



Orthis tubulostriata H.I 



Orthis eminens H... 



Orthis multistriata H. 



Orthis resembling subcarinata H. 



Strophodonta variastriata Con 



Strophodonta variastriata, var. arata H. 



Strophonella Headleyana H. 



Strophonella punctulifera Con 



Strophodonta Beckii H. 



Streptorhyrichus Woolworthana H. 



Strophomena radiata Vanuxem 



Strophomena rhomboidalis Wahl 



Spirifer cyclopterus H. 



Spirifer macropleurus Con 



Spirifer arrectus H. 



Spirifer pyxidatus, H. , 



Spiriferina perlamellosus H. 



Cyrtina Dalmani H. 



Nucleospira ventricosa H. 



Rhynchonella pyramidata H. 



RhynchoneUa formosa H. '. 



Eatonia medialis Vanuxem 



Ccelospira concava H. 



Ccelospira imbricata H. 



Meristella laevis Con 



•Meristella arcuata H. 



Pterinea communis H. 



Platyceras platystomum H., et al. sp.?.. 

 Leperditia 



Proportion in 



500 

 Individuals. 



5 

 11 



18 



1 



16 



128 



10 

 4 



1 

 23 



9 



3 

 20 



2 

 83 



4 

 91 



20 

 2 



3 



5 



10 



3 



1 

 21 



3 + 2 



Number of ad- 

 ditional speci- 

 mens collected. 



1 

 13 



1 

 2 



22 



1. Represented by fragmentary valves, casts or impressions, etc. 2. Repre- 

 sented by complete valves, casts impressions, etc. 3. "Worthy of special men- 

 tion in notes following. * Including P. althea H, P. arta R. . 



