BRACHIOPODA. 25 



A subordinate division of this section is the 



(1) Hungerfordi-type, in which the fold and sinus are low, often obso- 

 lescent, the outline suborbicular and the cardinal area compressed laterally 

 and incurved; dental lamellae prominently developed. This type is repre- 

 sented by 



S. pramonens, sp. nov., Niagara group. 



S. Hungerfordi, Hall, Lower upper Devonian. 



To the same division belongs the Russian species, S. Anossofi, de Verneuil, 

 which TscHERNYSCHEW Considers as probably identical with S. Hungerfordi and 

 an important index fossil of his uppermost middle Devonian fauna on the west 

 slope of the Urals.* 



Here must also be placed the Spirifer Mosquensis, Fischer, from the Carbonif- 

 erous limestone of Miaschkowa, Russia, and the type of the genus Choristites, 

 Fischer. Spirifer Grimesi, Hall, of the Burlington limestone resembles this 

 Russian species in external form, but lacks the prominent development of the 

 dental lamellae and the simple lateral plications possessed by S. Hungerfordi 

 and S. Mosquensis. In our opinion, if the term Choristites is to be admitted 

 with subgeneric significance, it should be restricted to this small group of 

 species beginning in the upper Silurian and ending in the Carboniferous. 



(b) Striatus-type. Forms having a great number of duplicate lateral plica- 

 tions, well developed, rarely acuminate fold and sinus, and narrow, usually 

 extended cardinal area. Species following closely the type of S. striatus are 

 not common in American faunas though they abound elsewhere. We have : 



S. striatiformis, Meek, Waverly sandstone. 

 S. Logani, Hall, Keokuk group. 



S. striatus, Martin, Coal measures. 

 S. Marcoui, Waagen, Coal measures. 



An important subsection of this group is composed of a series of forms 

 representing successive stages in a line of development, which diverged early 

 from the Striatus-stock and eventuated in some extravagant expressions of 

 this type. 



* Die Fauna des mittlei-eii und obei-en Devon am West-Abhange des Urals, pp. 174, 175. 



