(Figures 1-9, 14-19, 21,22,28-30, 32-35 by G. 
Legend, j. Cardinal process, 
a. Adductor scars. 
PLATE XVb. 
i. Simpson; 10-13, 24-26, 36, 37 by R. P. Whitfield; 20, 23, 27, 31 by E. Emmons.) 
r. Diductor scars. 
Genus STROPHEODONTA, Hall. 
(See Plates XIII, XIV, XV, XX.) 
Page 284. 
Stropheodonta (Douvillina) arcuata, Hall. 
Fig. 1. The interior of a pedicle-valve ; showing the cavity in the cardinal area as left by the removal of 
the cardinal process, the thickened, sharply defined and elevated muscular area. 
Fig. 2. The interior of the brachial valve. 
Fig. 3. The same enlarged, to show the character of the cardinal process, the small crural plates and 
divergent muscular ridges. X 2. 
Upper Devonian, Lime Creek , Iowa. 
Stropheodonta variabilis, Calvin. 
Figs. 4, 5. Opposite sides of the same specimen ; showing the contour and surface ornamentation. X 2. 
Fig. 6. The interior of the brachial valve; showing the cardinal process and divergent muscular ridges. 
X 2. 
Upper Devonian. Lime Creek, Iowa. 
Stropheodonta (Douvillina) Cayuta, Hall. 
of a pedicle-valve ; showing the sharply defined, tl 
ts subdivisions. 
Fig. 8. The interior of a brachial valve ; showing the muscular ridges. 
Chemung group. Tioga county, Pennsylvania. 
Stropheodonta (Douvillina ?) inasquistriata, Hall. 
Fig. 9. The interior of a pedicle-valve ; showing the greatly thickened lateral margins of the muscular im¬ 
pression. 
Hamilton group. Canandaigua Lake, N. Y. 
Genus STROPHONELLA, Hall. 
(See Plate XII.) ' 
Page 290. 
Strophonella cal at a, Hall. 
Fig. '10. The interior of a brachial valve in an unusually fine state of preservation. The flabellate muscular 
scars have the form usual to this genus and similar to that characterizing Douvillina. The 
crenulations of the hinge-line do not extend to the extremities of the cardinal area; a feature of 
frequent occurrence in many of the earlier species of Stropheodonta. The impressions of the 
pallial sinuses are also distinctly shown. 
Chemung group. Near Addison, N. Y. 
Genus CHONETES, Fischer de Waldheim. 
(See Plate XVI.) 
Page 303. 
Chonetes Flemingi, Norwood and Pratten. 
Fig. 11. The interior of a pedicle-valve; showing the character of the muscular scars and the internal 
openings of the spine-tubes beneath the cardinal area. X 3. 
Coal Measures. Illinois. 
Chonetes Smithi, Norwood and Pratten. 
Fig. 12. The interior of a brachial valve; showing the four scars of the adductor muscles. X 2. 
