PLATE XVb— Continued. 



Strophalosia radicans, Wiiichell. 



Fig. 27. A peiliele-valve, attached by its entire outer surface ami spines U> a Fistdlipuba. X 2. 



Fig. 28. A pedicle-valve, situated in a cavity among the ))olypite8ot .<4ce)-()«?aWa i>aTOrfso7ji. There is a slight 

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

 cai'dinal margin ci-eeping 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 liy the matrix 

 of the specimen. These latter spines appear to increase slightly in iliameter 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 Davidsonl, to which is attached a pedicle-valve of 

 this species ; its adherent spines lunning 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 

 ai-eas 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 infei-nal cast of a peilicle-valve, which shows the scar of attachment and iniiiressions of the 

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

 Chemung group. Coneioango, N. Y. 



Strophalosia scintilla, Beecher. 



Fig. 32. A specimen retaining both valves, attached to the surface of ySpM'i/er Maricmensis. This specimen 



shows no trace of spines. X 6. 

 Fig. 33. Another specimen which retains both valves, attached to a brachial valve of ProducteUa 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 Synngothyris Hannibaleiisis ; 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 Spirifer Marione^isis. This specimen is peculiar in showing 

 spines on the surface of the brachial valve. It occurs in aseociat'on with S. .icintilla, and it 

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



Strophalosia Cornelliana, Derby. 



Fig. 36. Posterior p.^rtion of the interior of the pedicle-valve ; showing the area, deltidiuni, teeth and mus- 

 cular scars. X 3. 



Fig. 37. The intei'ior of an imjierfect brachial valve which retains the cardinal process, and shows the 

 muscular scars and brachial impressions. X 3. 

 Coal Measures. Bomjardim, Brazil. 



