PLATE XVB— Continued. 



Strophalosia radicans, Wiuchell. 



Fig. 27. A pedicle- valve, attached by its entire outer surface and spines to a Fistdliphra. X 2. 



Fig. 28. A pedicle-valve, situated in a cavityamong-thepolypites of ^certrato-ia Damdsoni. There is a slight 

 attachment by the apex of the valve, Vjut fixation is mainly effected by the spines, those on the 

 cardin.al margin creeping along the surface of a polypile, and several of those which are on the 

 body of the valve crossing the cavity, their extremities being somewhat obscured by the mati-ix 

 of the specimen. These lattei' spines appear to increase slightly in diameter from the surface 

 of the shell outward, and their surface is marked with fine concentric annulations. X 3. 



Fig. 29. The calyx of a single polypite of Acervularia Davidsoni, to which is attached a pedicle-valve of 

 this species ; its adherent spines running between the septa of the coral. X 3. 



Fig. 30. An attached specimen, which retains the concave brachial valve in position, and shows the cardinal 

 areas and deltidia of both valves. X 3. 



Hamilton group. Little Traverse Bay, Michigan. 



Strophalosia hystricula, Hall. 



(See Plate XVII, figs. 29, 30.) 

 Fig. 31. An intei'nal cast of a pedicle-valve, which shows the scar of attachment and impressions of the 

 bases of spines over the body of the shell. X 3. 

 Chemung group. Coiiewango, N. T. 



Strophalosia scintilla, Beecher. 



Fig. 32. A specimen retaining both valves, attached to the surface of Spirifer Marimiensis. This specimen 



shows no trace of spines. X 6. 

 Fig. 33. Another specimen which retains both valves, attached to a brachial valve of Productella pyxidata. 



The spines about the margin should have been represented as belonging to the lower, not to 



the upper (brachial) valve. X 6. 

 Fig. 34. The interioi- of a pedicle- valve attached to the surface of Syringothyris Hannibalensis ; showing the 



few short spines which characterize the species. X 4. 

 Choteau limestone. Pike county. Missouri.' 



Strophalosia, sp. ? 



Fig. 35. A very small specimen attached to Spiriftr Mariojiensls. This specimen is peculiai' in showing 

 spines on the surface of the brachial valve. It occurs in association with S. scintilla, and it 

 may possibly prove the young of that species. X 8. 



Strophalosia Cornelliana, Derby. 



Fig. 36. Posterior portion of the interior of the pedicle-valve ; showing the area, deltidium, teeth and mus- 

 cular scars. X 3. 



Fig. 37. The interior of an imperfect brachial valve which retains the cardinal process, and shows the 

 muscular scars and brachial impressions. X 3. 

 Coal Measures. Bomjardiin, Brazil. 



