PLATE 23. 



Piige 



Fig*. 1-3, 9-11. Prodictella navicella , 15(> 



1, 2. Ventral views of two iiulivicluaU, from the Coruiforous limestone. 



3. Profile view of specimen flg. 1. 



9 - 11. Dorsal, ventral and profile views of a more elongated speuimen, from the Hamilton 

 group. 



Figs. 4, 5. PrODUCTELLA SUBACnLEATA? 154 



4. Ventral valve of a specimen, from the Fulls of the Oliio, showing spine-bases and one long spine. 



5. Interior of n dorsal valve of a similar cliaiacter, from East Victor, >!ew York. 



Pigs, (j -8. PaoDUCTELLA 8PJN ULICOSTA ?=/'. ihuiiiardiana 1(50 



6. 7, 8. Ventral, profile and cardinal views of a specimen from the Corniferous limestone near 



Louisville, Ky. 



Figs. 12-24. Prodi t-TELLA truncata 100 



12. Interior of ailorsal valve, enlarged to two diameters, from the Marcellus shale. 



13. An enlargement of a portion of the interior of a dorsal valve, show ing the cardinal process. 



14. An impression of the exterior of the dorsal valve, allowing the area of both valves. 



15. View of a vx-utral valve preserving several of the spines; from the MurcelUis shale. 



16. The exterior of a dorsid valve, from the limestones of the Marcellus shales. 



17. A ventral valve, of small size, having the beak but slightly truncated. 



18. 19, 20. Ventral, cardinal and profile views ol a sui:ill individual, having a large truncation; 



from the limestones of the Marcellus slialcs, enlarged to three diameters. 

 21,22. Interiors o<" dorsal valves, 

 ii. An impression of the dorsal valve,, and the area and be»k of the ventral valve, showing a 



narrow deltidium. 



24. A ventral view of a specimen which is somewhat largely truncate. Figs. 21 - 24, are from 



siiecimeiis from the Hamilton group. Figs. 12, 14-17, 21-23, are eiilarged to two 

 diailieters; fig. 13 to six diameters, and fig 24 to three diameters. 



Figs. 25-^. (35-37). Prodlctella spinulicosta 160 



(All the figures of natural size except fig. 26.) . — ^ -. 



25. The interior of a dorsal valve. 



26. An enlargement of a portion of the above to three diameters to show the cardinal process. 



27. A ventral valve of a small broad form. 



28. Ventral view of an individual of larger size. 



29. Profile of the same. 



30. Cardinal view of the same. 



31. A smaller individual imbedded in the rock, and showing .spines attached. 



82. Profile view of a specimen from the Tully limestone; probably of this si)ecies. 



33. Caidinal view of tlie same. 



34. A fragment of shale with crushed specimens of this species, preserving the slender spines. 



35. A ventral view of a spocimen from the limestone of the Marcellus shale, which clo.sely 



resembles the P. skumardiana from the calcareous bands below the Burlington limestone. 

 30. Ventral view of a specimen ol P. thumardiana, from Burlington, Iowa. 



37. Profile of the same. 



Figs. 38-40. Pboductklla du.mosa 162 



38. Ventral view of a small specimen. 



39. Profile of the same. 



40. Ventral view of a larger siieciraen, showing the base of spines remaining, and the pustules 



becoming elongated and a.ssuming the form of costic. The specimen is a little crushed. 



Figs. 41 - 44. Productella tuli.i a 164 



41. An impression of the exterior of a dorsal valve preserving the cardinal process; from the 



Hamilton group. 



42. A dorsal valve of larger size; fi-om the shale of the Hamilton group. 



43. A large dorsal valve from the Tully limestone. 



44. An enlargement of the i)ustules and surface striaj, as shown in figs. 41 & 42. 



Figs. 45, 46. Productella exanthemata 163 



45. 46. The interiors of the dorsal valves of two individiial.-i, natural size. 



Figs. 47, 48. Productella sp ? 165 



47. The interior of a dorsal valve, natural size. 



48. A profile of the same. 



Fig. 49. Productella subalata 165 



49. Ventral view of an individual, from the calcareous shale at Rock Island, Illinois. 



