IDENTIFICATIONS) FROM ONE TYPE OF SEDIMENTS 427 



Genera and Subgenera identified from but one Type of Sediment 



In the following table are listed the twenty-six genera and subgenera 

 which have been identified from but one type of sediment. lu all they 

 "form 41 per cent of the total number of these larger groups which have 

 been recognized, but they include within their number twelve genera 

 which are represented only by single species in single faunules. Of the 

 more or less cosmopolitan, genera, therefore, only 14 (or 22 per cent) 

 appear to be confined to one type of sediment. 



Table II. — Genera and siihgenera of Camhrian and related Ordovician Braelii- 

 opoda identified from hut one type of sediment, (jiving nu/inhers of speeies 

 and localities. 



Genera and subgenera, those represented 

 by single speeies in single faunules be- 

 ing placed in this column only, together 

 with a statement as to the inclosing 

 sediment. 



Inclosing sediment. 



Lime- 

 stone. 



Shale. 



Sand- 

 stone. 



Acrothcle (RedUchella) (lime- 

 stone) 



Bicia 



Clarkella (limestone) 



Ciirticia (sandstone) 



DearJiornia (limestone) 



Delgadella (shale) 



Discinolepis 



Eostropliomena 



Finkelnh'urgia 



Helmersenia 



Keyserlingia 



Lingulella (Leptemholon) 



Mickwitzia 



Neoholus 



Oholella (Glyptias) 



Oholus {Miekivitzella) 



Oholus (Schmidtia) 



Philhedra (limestone) 



Protorthis (Loperia) (sandstone) 



Qiieheeia (limestone) 



Sehizopholis (sandstone) 



Schuchertina (limestone) 



Siphonotreta^ 



Sicantonia 



Volhorthia (limestone) 



Wynnia (shale) 



Totals for limestone 



Totals for shale 



Totals for sandstone 



X 



Number 



of 

 species 

 in each 

 genus. 



10 



oS 



« > fl5 

 <s Sep: 



C <0 ^ 'V^ 



2 

 2 



21 

 3 

 3 

 6 



18 

 3 

 2 



13 

 37 



23 

 2 



31 

 •> 



108 



" In Monograph 51 of the U. S. Geological Survey on the Cambrian Brachiopoda a 

 poorly preserved Lower Cambrian shale species is very tentatively referred to this typi- 

 cally Ordovician genus under the name of Siphonotreta ? dubia, but it is from a single 

 faunule and is described by Mr. Walcott as probably representative of a new type. 



