DESCRIPTION OF PLATE V CONTINUED. 497 



Page. 

 Fig. 7. Marginifeka jiukicata 373 



An imperfect specimen of the same character as the foregoing, but one which retains the 



original spinose surface. 

 Ventral valve seen from above. 

 Maroon formation: Southeast of Italian Peak, Elk Mountain region (station 2280). 



Figs. 8 and 8a. Marginifeka wabashensis var 375 



A small but typical specimen referred to this species. The specimen is verj^ imperfect, 



but it is the best which our collections contain. 

 Fig. 8. Specimen seen from above, considerably restored. 



8a. Side view. 

 Hermosa formation: Silver Creek, San Juan region (station 2220). 



Figs. 9 to 9c. Marginifeka h aydenensis 380 



A very characteristic specimen of the type upon which the species is based. 

 Fig. 9. Dorsal view. 

 9a. Ventral view. 

 9b. Posterior view. 

 9c. Side view. 

 Near Grand River, Colorado (?) (station 2324). 



Figs. 10 to 10b. Makginifera haydenensis 380 



Another very characteristic example which is elongated in shape, instead of transverse. 

 Fig. 10. Ventral valve seen from above. 

 10a. Side view. 

 10b. Posterior view. 

 Near Grand River, Colorado (?) (station 2324). 



Figs. 11 and 11a. Makginifera haydenensis 380 



Another specimen belonging to the same species. The two specimens previously figured 

 have been almost devoid of strise. The stripe of the present specimen are q,uite distinct, 

 but very irregular. The difference is not believed to be specific. 

 Fig. 11. A'entral valve seen from above. 



11a. Side view. 

 Near Grand River, Colorado (?) (station 2325). 



Figs. 12 axd 12a. Marginifera inorata 379 



A well-preserved specimen belonging to this species. 



Fig. 12. Specimen seen from above. The strise in the figure are represented as too coarse. 



12a. Side view. 

 Weber shale: Little Ella Hill, Leadville district (station 2253). 



Figs. 13 to 13b. Marginifera ingrata 379 



An internal cast of a ventral valve referred to this species. The striation is somewhat 

 coarser than on the specimen previously figured, but it is represented as somewhat too 

 coarse in the figure. 

 Fig. 13. Specimen seen from above. 

 13a. Anterior view. 

 13b. Side view. 

 Weber formation (?) : Horseshoe Gulch, Leadville district (station 2259). 

 14364— No. 16—03 82 



