BRACHIOPODA. 285 



Shell-substance impunctate externally, but the inner laminoe are sparsely 

 perforated. 



Type, Stringocephalus Burtini, Defrance. Middle Devonian. 



Observations. This old and well known genus has been discussed by many 

 Wi iters, but to King, Suess and Quenstedt our knowledge of its internal 

 structure is especially due. Its characters are extravagant and its com- 

 position is peculiar and unique, the genus standing quite apart from other tere- 

 bratuloids. Whence its origin is still a mystery. The duration of the type 

 was brief, though its development was abundant and characterized a distinct 

 horizon of the middle Devonian, the " Stringocephalus beds." Its presence, 

 however, has not been widely known outside of Germany and England, and 

 hence its recent discovery by Whiteaves in the Mackenzie River Basin of 

 British North America, is of much interest. Here it is associated with various 

 middle Devonian species. 



Authors are pretty generally agreed that the different specific designations 

 which have been suggested for slight variations in form, etc., are based upon 

 minor characters, insufficient to separate them from the type-species, S. Burtini, 

 The S. Bohemicus, Barrande,* is a much earlier form (F.,,) whose generic char- 

 acters are entirely uncertain. 



* SystSme Silurien, vol. v, p. 218, pi. 83, iv. 



