318 E. Billings on some cfthe 



Potsdam Sandstone. One species nndescribed discovered 

 by Dr- Shumard in Texas, 



Calciferous Sandrock. Two Species, G. caldfera and an- 

 other large nndescribed species of wbich I have some fragments. 



Chazy Limestone. Two species, 0. longirostra and C. var- 

 ians. This Journal, Vol 4. 



Black River. Two species. C. Panderi and C. Volborthi, 

 This Journal, Vol. 4. 



Trenton. Three species. C. extans, G. nudeata, and G. cus- 

 pidata. These three were described by Prof. Hall in Vol. 1, Pal. 

 N. Y., under the genus Atrypa. 



Of the ten species known in America seven occur below the 

 Trenton Limestone. The Texas species is particularly interest- 

 ino- on account of its association with primordial trilobites. The 

 following- are the fossils which are found with it in the same beds. 

 This list is copied from Barrande's elaborate memoirs on the 

 Primordial Zone and Taconic system in the Bulletin of the Geo- 

 loo-ical Society of France.^ It was prepared for him by Dr. 

 Shumard. 



" Agnostus, very similar to Agn. Orion. Billings. 



" Conocephalites. 



" Lonchocephalus (^BatJiyurus) amiatus f Billings. 



" Arionellus. Two species very distinct, of which one resem- 

 bles a form that occurs in the third magnesian limestone of 

 Missouri. 



<' Viscina. — One small species. 



" Orthis Goloradoensis. Shumard. 



<' Sps. indetJ' 



The above list so far as it goes exhibits an association of orga- 

 nic types similar to that which occurs in the limestones at Point 

 Levi. In no country in any part of the world has such an assem- 

 blao'e been discovered above the Primordial Zone, or at least above 

 the very base of the Lower Silurian, and the genus Gamerella is 

 therefore one of the most ancient of the brachiopodous forms of life. 



Camerella Calcifera, N. sp. 



Description — This species varies from four to nine Hues in 

 width. The proportional length varies from a little less to a little 



* Documents anciens et nouveaux sur lafaune primordiale et le SysUme 

 Taconique en Amerique^ par M. J. Barrande. Bui. Soc. Fr., 2nd Series, 

 Vol. 18, p. 203. 



