Bkkdk.] Carboniferous Invertebrate*. 179 



Derbya eroasa, I p. 68. | 



11. ll/>. Externa) and internal views, respectively. Natural size. 



Derb}/ a bilobaf 



12. Specimen, perhaps of this species, from Lecompton. (Rogers.) 



/>> rbya keokuk, | p. 63;) 



13. Brachial valve. Natural size. 



Hydreionocrinus aubsjnuatus, (p. 43.) 



14. Basal view of calyx. Natural size. 



PLATE IX. 

 Chonetes granuUfer t (p. 69.) 



1. External view of pedicle valve. Natural size. 



1//. Internal view of brachial valve, showing radiating ridges, indications of 



the brachial areas, and the granular inner surface. 

 lc. External view of a peculiar specimen of this species, showing the auricu- 

 lation. Natural size. 

 Chonetes globe r, i p. 68.) 



2. Exterior of pedicle valve. Natural size. 

 Chonetes mesolobus, (p. 71.) 



3. Pedicle valve. Natural size. 



36. Interior of brachial valve, showing the cardinal process, brachial and 

 other markings. Enlarged. 

 Chonetes vemeuilianus, (p. 72.) 



4. Pedicle valve of long-eared variety. (After Meek.) 

 4/). Same of short-hinged specimen. Natural size. 



4e. Interior of brachial valve, showing the markings. Natural size. 

 4' . Interior of pedicle valve, showing adductor and diductor scars. Natural 

 size. 



Productus [>( rU nuis, < p. 83.) 



5. Pedicle valve. Natural size. 



56. Brachial valve, interior view, markings removed. Natural size. 



5c. Longitudinal section, showing the relation of the valves in this species. 



Productus symmetricu8i (p. 86.) 



6. Interior of brachial valve, showing adductor markings, lateral ridges, and 



mesial ridge. Natural size. 

 66. Pedicle valve, partially covered by matrix. Natural size. 

 Productus nebrctscf nsfs, (p. 84.) 



7. View showing the curvature of the beak and the relation of the pedicle 



to the brachial (or flatter) valve. Natural size. 

 7// and Id. Lateral and full view of pedicle valve of the same specimen. 

 If. Cast of specimen, showing adductor and diductor scars. Natural size. 

 le. Pedicle valve, showing the nature of the spines when not removed. 



Natural size. 

 If. Interior view of brachial valve, showing the cardinal process, large pit 



immediately back of it, mesial septum, adductor markings, and a 



dim outline of the brachial marks. Natural size. 



