PLATE LX. 



Page. 

 Fig. 1. Obolus (Lingitlepis) acuminatus var. meeki 444 



1. Ventral valve, x 3. 

 la. Dorsal valve, x 3. 



Fig. 2. Obolus (Liiigulella) desideratus 445 



2. Ventral valve, x 6. 

 2a. Dorsal valve, x 6. 



Fig. 3. Dicellomus nana 447 



3. Ventral valve, from Gallatin Range, x 6. 



3a. Dorsal valve, from Little Rocky Mountains, Montana, x 6. 



36. Ventral valve (type specimen of Meek and Hayden) from Black Hills, South 



Dakota, x 6. 

 3c. Cast of interior of ventral valve, from Little Rock Mountains, Montana, x 6. 

 3d. Cast of interior of ventral valve (type specimen of Meek and Hayden), from 



Black Hills, South Dakota, 

 Fig. 4. Dicellomus politus 446 



4. Interior of dorsal valve, x 6. 

 4a. Interior of ventral valve, x 6. 



Fig. 5. Iphidea soulptilis 447 



5. Summit view of ventral valve, x 4. 

 5a. Side view of fig. 5. x 4. 



5b. View of the broken false area and pseudo-deltidinm of fig. 5. x 4. 

 5c. Surface of fig. 5, greatly enlarged. 

 Fig. 6. Jphidea sp. undet 449 



6. Dorsal valve described in the text, x 4. 



468 



