EXPLANATION OF PLATE X. 



Fig. 1. SriRiFici; cvmhuatus. (Pago 13-^.) 



a. Dorsal view of an example Iroiii ucar Santa Fc. 



T). Siniilai- view of auotber example from Northern Missouri. 



c. Ventral view of the sa;!'.e. 



d. Lateral view of th ^ same. 



Fig. 2. Spihii'KR (Maistinia) gi.auek var. C()NTi;actus. {Page loG.) 



a. Ventral view of an exami^le, near average size. 



6. Dois.il view of the same. The fpecimen lias been a little compressed. 



c. Lateral view of a large example ; a little distorted by growth. 

 Fig. 3. Spirifer (Mautinia) planocoxvexu.s. (Page 135.) 



a. Ventral view of a specimen, enlarged. 



h. Dorsal view of the same. 



c. Lateral view of the same. 

 Fig. 4. Spirifeuixa Kentuckensi.s. (Page 138.) 



a. Ventral view of u specimen, enlarged ; one hinge-extremity naturally longer than the 

 other. 



6. Posterior view of the same. 



c. Dorsal view of another example. 

 Fig. 5. Spirigera planosulcata. (Page 143.) 



a. Ventral view of average size of those contained in the collections. 



t. Dorsal view of the same. 



c. Lateral view of the same. 



d. Dorsal view of another example. 

 Fig. 6. Spirigera subtilita. (Page 141.) 



a. Ventral view of an example of ordinary size and form. 

 h. Dorsal view of an example proportionally shorter, 

 e. Lateral view of the same. 

 Fig. 7. Retzia mormonii. (Page 141.) 



a. Ventral view of an example of ordinary size. 

 6. Dorsal view of the same, 

 c. Lateral view of the same. 

 Fig. h. Spikiferina octopi.icata. (Page 139.) 



a. Ventral view of an example a little below average size. * 

 6. Ventral view of another exa'.nplo ; test removed by exfoliation, 

 c. Front view of the same. 

 Fig. 0. HicMiPRONiTKS CRiNiSTRiA. (Page 124 ) 



a. Dorsal view of an example somewhat compressed. 

 Fig. 10. RiiYNCiioxELLA metaxlica. (Page 129.) 



a. Ventral view, natural size. 



b. Dorsal view of the same. 



c. Lateral view of the same. 

 (/. Front view of the same. 



