EXPLANATIONS OF PLATE II. 



PAGE- 



Fig. 1. a, b, C. . . . CHiENOMYA LEAVENWORTHENSIS. 43 



1 a. Side view, with portions of the shell removed, so as to show the muscular scars, and faintly 

 sinuous pallial impression. 



1 b. Dorsal view of an internal cast, showing the wide posterior gap. 



Fig. 2. a, h. . . . Cn/EXOMYA Cooperi. .... 44 



2 a. Side view of a cast, with a little of the posterior margin broken away. 



2 b. Dorsal view of same, showing a distinct depression along the hinge left by an internal thicken- 

 ing of the cardinal margin. 



Fig. 3. .... Pleurophorus ? subcuneata 61 



Fig. i. a, b YoLBiA subscitula. . .... CO 



4 n. Side view of a cast, left valve. 



4 b. Dorsal view of same. 



Fig, 5. a, h, c. . . . . EuMiCROTis Hawni. ....... 54 



!j u. Internal cast of a left valve (ribs obscure). 



5 b. Profile anterior view of a left valve. 



5 c. Internal impression of a right valve showing the deep byssal sinus at (s). 



Fig. a. a, b. . . . EuMiCROTis Hawni, var. ovata. 55 



C a. Cast of the exterior surface of a left valve, showing the very short hinge line, and distinct 



costre of this variety. 

 G b. Anterior profile view of same. 



Fig. 7. a, b, c. . . . . Myalina permiana. ...... 52 



7 a. Internal cast of a left valve, usual form. The impression of the hinge area shown in outline 



in this figure, is added from another specimen. 

 7 b. Anterior view of same. 



7 c. Cast of a broader vaiiety of s.ame species not showing the cardinal area. 



Fig. 8. a, b, e, d. . . Myalina aviculoides. 51 



8 a. Cast of the exterior of a left valve, adult size. 

 8 b. Anterior view of same. 



8 c. Cast of exterior of a young specimen. 

 H rf. Anterior view of same. 



Fig. 9. . . . Aviculopecten McCoyi, (ext. cast left valve). .... 50 

 Fig. 10. . . . Aviculopecten ? (cast left valve). .... 50 



Fig. 11 O, 6 SCHIZODUS OVATUS .59 



11 «. Cast, left valve, side view. 



11 //. Dorsal view of same. 



Fig. 12. rt, 6 Bakevellia PARVA 51 



12 a. Cast of left valve, side view, natural size. 



12 i. Cast of another specimen enlarged. 



Fig. 13. a, b Pleurophorus CAi.nouNi. ...... G2 



13 a. Internal cast, side view, showing a cast of the anterior muscular impression, with a furrow 



behind it, left by an internal ridge. 



13 b. Dorsal view of the same, being a cast of the interior of the two v.alves as seen partly opened. 



Fig. 14. a, b. . . . Nautilus eccentricus. ... .05 



14 o. Side view of an internal cast, showing the septate and non-septate portions 

 14 6. Dorsal view of same. 



