PLATE XCVI 



PAGE 



Figs. 1-3. MESOMPHALUS HARTLEYI Ulrich and Bassler n. gen. and sp 523 



1, 2. Ventral and posterior end views of a female individual. X 20. 

 3. Highly magnified view of the surface of original of fig. 24, pi. xcv. 



Figs. 4, 5. MESOMPHALUS SUBMARGINATA Ulrich and Bassler n. sp 523 



Lateral and ventral edge views of the type specimen. X 20. Helder- 

 berg formation, Keyser member, Cumberland. 



Figs. 6-9. CTENOBOLBINA ? DENTICULATA Ulrich and Bassler n. sp 524 



6. Lateral view of one of the type specimens, a left valve with a portion 



of the flange broken away and the surface simply granulose. 

 X 20. 



7. Dorsal edge view of the same specimen. X 20. 



8. A right valve showing pits between the granules of the surface. 



X 20. 



9. Ventral edge view of same. X 20. 



Helderberg formation, Keyser member, Cumberland. 



Figs. 10-12. CTENOBOLBINA ? DUBIA Ulrich and Bassler n. sp 525 



10. Left side of complete carapace. X 20. 



11, 12. Ventral and posterior edge view of same. X 20. 



Helderberg formation, Keyser member, Cumberland. 



Figs. 13-15. BOLLIA AMERICANA Ulrich and Bassler n. sp 525 



Lateral, ventral and posterior views of a left valve. X 20. Oriskany 

 formation, 21st Bridge. 



Figs. 16, 17. BOLLIA CURTA Ulrich and Bassler n. sp 526 



Side and ventral views of a left valve of this well-marked species. 

 X 20. Oriskany formation 21st Bridge. 



Fig. 18. BOLLIA IRREGULARIS Ulrich and Bassler n. sp 527 



Lateral view of right valve. X 20. Helderberg formation, New Scot- 

 land member, 21st Bridge. 



Fig. 19. BOLLIA JUGALIS Ulrich and Bassler n. sp 527 



A left valve showing the ventral coalescence of the median and mar- 

 ginal ridges. X 20. Oriskany formation, 21st Bridge. 



Figs. 20-22. BOLLIA UNGULA Jones 528 



Lateral, ventral and posterior views of a left valve. X 20. Oriskany 

 formation, 21st Bridge. 



87 



