PLATE LVIII 



PAGE 



Figs. 1-10. SPIRIFER MUCRONATUS VAR. POSTERUS Hall and Clarke 599 



1. Ventral valve of medium size. National Road, east of Hancock, 



1149 to 1274. 



2. Dorsal valve with extended cardinal angles. National Road, west 



of Tonoloway Ridge. 



3. Dorsal valve. Associated with fig. 2. 



4. Cast, of interior of a very large dorsal valve. Woodmont, 1032. 



5. Cast of interior of ventral valve of medium size. There is no 



median septum but muscular scar is divided by an impressed 

 line. Yellow Springs Road, 3 miles east of Berkeley Springs, 660 

 feet west of beginning of section. 



6. Cast of interior of large ventral valve with greatly extended ex- 



tremities. Woodmont, 1032. 



7. Cast of interior of dorsal valve differing from prevailing form. 



Woodmont, 1000. 



8. Enlargement of cast of interior of dorsal valve showing muscular 



scars. X 3. Western Maryland Railroad, 2 miles west of 

 Pawpaw, 1300. 



9. Cast of interior of ventral valve of young individual. National 



Road, east of Hancock, 690. 



10. Enlargement of a portion of exterior of valve of young individual 

 showing ornamentation. X 10. National Road, east of Mill- 

 stone, 795. 



Jennings formation, Woodmont member, Ithaca fauna. 



Figs. 11-23. SPIRIFER (DELTHYRIS) MESACOSTALIS Hall 601 



11. Ventral valve of a very small individual. Near Deer Park. 



12. A larger ventral valve. National Road, Polish Mountain. 



13. Enlargement of a part of surface of ventral valve showing median 



rib and sharp lamellose concentric markings. X 2. Same 

 locality. 



14. Small dorsal valve. Same locality. 



15. Small ventral valve. X 2. The ribs are made to appear too sharp 



and the concentric lines too angular. Near Pawpaw, W. Va. 



16. Small dorsal valve. Near Deer Park. 



17, 18. Cast of interior of small ventral valves. X 2. Same locality. 



19. Cast of interior of small dorsal valve. X 2. Same locality. 



20. Cast of interior of ventral valve. Mountain Lake Park. 



21. 22. Cast of interiors of ventral and dorsal valves of usual size. 



Williams Road, Polish Mountain, 1660. 



23. Cast of interior of large ventral valve having extended cardinal 

 angles. 4700 feet northeast of Sunnyside. 



Jennings formation, figs. 21, 22 Parkhead member, balance 

 Chemung member. 



141 



