NQETII AMERICAN PALEONTOLOGY. 



279 



Walcott, Charles Doolittle — Continued. 



And also the table ou page 62, as follows : 



Zoologlc resume. 



Algae 



Spongias 



llydrozoa ■ 



Criuoidea 



Annelida 



Brachiopnda 



Lamellibranchiata 



Gasteropoda 



Pteropoda 



Crnstacea 



Pcecilopoda 



Genera. Species. 



92 



On page 63 a table of the classification of the North American Cambrian rocks 

 shows that the Cambrian includes the Potsdam sandstone and the Lower 

 Calciferous of the New York Survey as its upper member, and the Paradox- 

 ides beds of Braiutree, Massachusetts, St. John, New Brunswick, and St. 

 John's, Newfoundland, as the basal member, and the Georgia formation as 

 the middle division. 



The geologic sections given in the introduction show the Cambrian system "to 

 have a total thickness of over I'S.OOO feet, and that its middle division has 

 a known fauna of 43 genera, represented by 107 species ; also that tbe Lower 

 Cambrian or Faradoxides fauna has 32 genera and 76 species ; that the Upper 

 Cambrian or Potsdam fauna includes 52 genera and 2128pecies ; that of the 

 393 species now known from the Cambrian rocks but very few pass up into 

 the Calciferous horizon of the Lower Silu'-' ^^O^dovician), and that the 

 faunas of the two systems are so dis^!; . , m their general facies, and also in 

 detail, that they are quite as readily separated as the Silurian and Devo- 

 nian, or the Devonian and the Carboniferous." 



Ninety species, eighteen of which are new, are described and illustrated, and 

 three new genera are pro^wsed— Xe2Jfomi<«s * (Spongise), Oryctocep]iahi8,\ 

 and Protijpm (Trilobita). The almost nuknown genera JEthmoplnilhim, 

 Meek (Spougia'), and O/cHoWes, Meek (Trilobita), are described ; and the 

 genus Microdiscus, Emmons (Trilobita) is redefined and based on auother 

 species, as its type species is considered to be an embryonic form of Trinu- 

 cleus concentric us. 



Paragraphs 119 and 120, page 57, state that : " Reviewing the Middle Cambrian 

 fauna as a whole, we find that it combines the characters of both the Lower 

 Cambrian and the Upper Cambrian faunas, and yet is distinct from either 

 of them. There does not appear to be an equivalent fauna in the Cambrian 

 system of Europe, either in Bohemia, the Scandinavian area, or in Wales. 

 The nearest approach to it is on the island of Sardinia." (See close of re- 

 marks on the genus EilnnophyUiim, p. 80.) 



"The conditions that developed the Middle Cambrian fauna appear to have 

 been largely peculiar to the American continent. During the deposition 

 of the St. John series of the Lower Cambrian or Paradoxides strata, we learn 

 from the European and eastern American section that the fauna was essen- 

 tially of the same type over the entire basin (Atlantic), and from the evi- 

 dence known to date that the fauna did not extend west of a line passing 

 northeast through eastern Massachusetts to New Brunswick and Newfound- 

 land." 



The illustrations are wood-cuts, and are very good of their kind. 



* Leptos (fine), mitos (thread). 

 t'Opuwrof (furrowed), and «-£(p«A// (head). 



