of Burlington^ loiva, and its Vicinity. 



233 



plates strong, projecting a little forward of the hinge-line. 

 From six to eight prominent plications on each side of the 

 mesial fold and sinus, which decrease regularly in size 

 toward the hinge extremities. Sinus rather broad and 

 deep, distinctly defined even to the point of the beak ; a 

 slightly elevated ridge extends along its bottom, and a cor- 

 responding depression along the mesial fold. 



Mesial fold prominent, and widely separated from the 

 plications. Surface marked by fine, lamellose, concentric 

 strisB, which arch upon the plications, and the ridge in the 

 mesial sinus, and doubly arch upon the mesial fold. 



Geological formation and locality. In beds Nos. 5, 6, 

 and the lower portion of No. 7, of the preceding sections, 

 Burlington, Iowa. 



List of described Fossils recognized in the Burlington Rocks. 



Gyroceras Burlingtonensis, 

 Euomphalus latus, 



" obtusus, 



Spirifer Grimesi, 

 " Forbesi, 

 " plenus, 

 " imbrex, 

 " incertus, 

 '• subrotundatus, 

 " extenuatus, 

 " biplicatus, 

 Rhynchonella Missouriensis V 

 Atliyris incrassatus, 

 Ortliis Swallovi, 



" Michelina, var. Burlingtonensis, 

 " inajqualis, 

 Chonetes Fischeri, 

 " Logani, 

 Productus arcuatus, 



" Fleming!, var. Burlingtonensis, 



" concentricus, 

 " Shumardianus, 



JOURNAL B. S. N. 11. 30 



MOLLUSCA. 



Owen, 

 Hall, 





Norwood and Pratten, 

 Hall, 



Shumard, 

 Hall, 



var. 



Norwood and Pratten, 

 Hall, 



var. 



Chemung. 

 Carboniferous. 

 Chemung. 

 Carboniferous. 



Chemung. 



Carboniferous. 



u 

 it 



Chemung. 



Carboniferous. 

 Chemung. 



