DESCRIPTION OF 







PLATE VI. 



Page 



Fig. 1. SPIRIFER MARIONENSIS. 511 



1 a, b. Ventral and dorsal views of a specimen of medium size. 



1 c. Cardinal view of the same, showing the narrow linear area. 



Fig. 2. PENTAMERES OCCIDENTALIS. 514 



2 a. Ventral view of an imperfect specimen. 

 2 b. Profile of the same. 



2 c. Interior, showing the hinge, the triangular cavity, etc. 



Fig. 3. ATRYPA ASPERA, var. OCCIDENTALIS. 515 



3 o. Dorsal valve of a specimen below the medium size. 

 3 b. Dorsal valve of a very ventricose specimen. 



3 e (= 3 c). Ventral valve of the same. 



8 d. Profile of the same specimen, showing the extreme convexity of the 

 ventral valve, and small elevation of the other valve near the beak. 



Fig. 4 & 5. ATRYPA RETICULARIS. 515 



4 a, b. Dorsal and ventral views of a small specimen. 



4 c. Ventral view of a larger individual. 



5 a, b, c. Dorsal, ventral and profile views of a very large individual. 



Fig. 6. EUOMPHALUS CYCLOSTOMU8. 516 



6 a. View of the summit of a specimen of the ordinary size. 

 6 6. View of the base of the same. 



6 c. Profile view, showing the elevation of the spire. 







