PLATE 13 



PiGs. Skenidium insigne (Hall) 



1,2,5,8. — Posterior, anterior, dorsal, and postero-dorsal 

 views of three individuals, showing characteristic ex- 

 ternal form. Figs. 1 and 8 show uncovered del- 

 thyrium, and spondylium. 

 3. — Dorsal interior, showing wide hinge-plate. 

 4. — Ventral interior, showing spondylium. 



Devonian (New Scotland), Indian Ladder, Albany 

 Co., N. Y. C.it. No. S2025. x 6. 



Finkelnburgia sp. 

 6, 1 1 . — ^Ventral exterior, and interior showing pseudospon- 

 dylium. 

 Ozarkian (Eminence, near top), S. slope of hill 

 4% to 5 miles S. of Potosi, Missouri. Wax impres- 

 sions from originals in U. S. Nat. Mus. Cat. No. 

 S60. x3. 



Finkelnburgia sp. 



7^ Ig. — Dorsal interiors, showing incurving brachiophore 



plates and subradial muscle impressions and strongly 



elevated ridges about each impression. 



Ozarkian (Huzzah Creek section, bed 7), 10 miles 



E. of Slideville, Missouri. Wax impressions from 



originals in U. S. Nat. Mus. Cat. No. S 58. x 3. 



Finkelnburgia armanda (Billings) 

 9, 10. — Dorsal internal mold, and wax impression taken 



from it. 

 12. — ^Wax impression of ventral exterior, showing sculpture. 

 15. — ^Wax impression of dorsal interior. This and fig. 10 

 show the simple cardinal process and the incurving 

 brachiophore plates, and the fulcral plates. Structure 

 much like that of Hebertella or Plectorthis. 

 Ozarkian (near base of Logan's B3) near Phillips- 

 burg, Quebec. Cat. No. S 2109. x 2.20. 



Fics. Finkelnburgia sp. 



13,1 7. — Dorsal and ventral exteriors of a silicified specimen. 

 16. — Dorsal interior, reverse of fig. 13, showing converg- 

 ing brachiophore plates and elevated seats of muscle 

 attachment. 

 19. — Ventral interior, reverse of fig. 17, showing pseudo- 

 spondylium. 

 Ordovician (Canadian), 3 miles S. E. of Rainy Mt., 

 Kiowa Co., Okla. Ulrich Coll., U. S. Nat. Mus. 

 x3. 



Finkelnburgia aflf. osceola (Walcott) 

 14. — Ventral internal mold, showing filling of delthyrial 

 cavity. 



Finkelnburgia appears to be the earliest genus in the 

 plectorthid line. 

 Ozarkian, Crawford Co., Missouri. Cat. No. S 62. 

 x3. 



Angusticardinia recta (Pander) 

 20, 22. — Ventral and dorsal views of this rhynchonelloid 



orthid. 

 2 1 . — Dorsal interior, showing brachiophores and their sup- 

 porting plates which unite at the floor of the valve 

 with the median ridge, forming a narrow notothyrial 

 orthid. 

 Ordovician ( Walchow, Glauconite ss., Bip) , Popovka, 

 near Leningrad, Russia. Cat. No. S 171. x 3. 



Angusticardinia striata (Pander) 



23. — View showing profile. 



Ordovician (Walchow, Glauconite ss.,B,3), Popovka, 

 near Leningrad, Russia. Cat. No. SI 70. x 3. 



220 



