PLATK XII— Continucii. 



Strophonella reversa, Hall. 



Fig. 16. View from the ln-achial valve; showing the uiiinterriipted area of the pedicle-valve. 



Fig'. 17. The exterior of the pedicle-valve. 



Fig. 18. The interior of a brachial valve ; showing the deeply bifurcated cardinal process and the muscu- 

 lar scars. 



Fig. 19. The interior of a pedicle-valve in which the muscular and vascular markings are very strong. 

 The car<linal area is seen to be without any ti'ace of deltidiuni, and the umljonal cavity has 

 been so completely filled by calcareous dejiositions about the lobes of the cardinal process that 

 the lattei- have broken and i-emain attached (i, i,) to the pedicle-valve. 



Fig. 20. The centi-al portion of the hinge, enlarged, from a .specimen which has been .somewhat weathei'ed, 

 thus exposing the vertical ridges which tei'iuinate in crennlations at the margin, and id.so show- 

 ing the limits of the deltidia. X 2. 



Upper Devonian. Rockford, Iowa. 



Steophonella c^lata. Hall. 



(See Plate XVb, fig 10.) 

 Fig. 21. A cast of the interior of the pedicle-valve ; showing the widely extended, crenulated hiuge-Iine, and 

 the very concave valve with strong muscular and vascular impressions. The points mai-ked k, 

 are the filling of the cavities beneath the area for receiving the extremities of the (cardinal 

 jirocess. 



Chemung group. JVear Elmira, N. Y. 



