V PLATE 42. 



Figs. 1 - 20. Spirifeiia disjincta i!4.'> 



(The references to this plate, on page 246, should be to plate 41.) 



1. A small narrow form retuiuing the shell. 



2. A cast of a young individual. 



8. Cast of a valve of usual form. 



4.5. Valves of small fonns, having the uardiual e.\treuiities short ami rounded; the hitter 



tigure showing the extension of the denial lamella! nearly to the front of the valve. 

 C. Cardinal view of a spcciiiK-ii having a very- high area and wide foranieu. 

 7, 8. Forms in which the cardinal area and foram;)ii are proiKirtionally narrow. 



9. 11. Individuals of the i>revailHig form retaining the shell. 



10. Cast of a broader form. 



12, 14, 1.5. Specimens showing extreme variation of muscular impressioii. 



13,19.20. Individuals showing great extension of the cardinal exlremitieo. Spiri/cra (Ihl- 

 thyrit) perlaia, Conrad. D. mspidata. Ilall. 



16. Cardinal view of the si>ecimen. fig. 15, showing shod thiekened denial lanielUe. 



17. Cast of a small individual, showing dentul lamella; extending to the front of the valve. 



18. Interior of a specimen pre^CTving a portion of the shell and showing the form of the louii- 



cular improssion. 



(The figures on^this plate are all ventral valves.) 



\ 



