PLATE LXXX. 

 Mytilarca pyramidata. 



I'agc i86. 

 Figs. 1, 2. Left side and anterior view of a cast of the interior. 



S<-hohaine grit. Schoharie, N. Y. 

 V\g. 3. The right side of a spe<'inien, somewhat smaller than the preceding. 



Schoharie grit. Schoharie, iV. Y. 



Leitodesma ? 



Pig. 4. An olieuure right valve of undetermined relations. 

 Chemung group. Salaiiumca, N. Y. 



SpHENOTUS (?) UNDATUS. 



PageSOe. 

 Fig. 5. View of a left valve as obtaine<l fi-om a gutta-percha impression in a natural mould. 

 Chemung gi-oup. Mansfield, Pa. 



ORTnONOTA RIGIDA. 



Page 481. 

 Pig. 6. A right valve showing the form and surface markings. 

 Chemung group. Near Ehnira, N. Y. 



MomOMORPHA ALTA. 



I'ngi! 278. 

 See Plate 37. 

 Fig. 7. The right side of a distorted specimen. 



Hamilton group. Pratt's falls, N. Y. 



Panenka mollis. 



Page 420. 

 Fig. 8. A specimen preserving both valves in conjunction, showing the form and surface characters. 



Mareellus shale. 

 Fig. 9. Cardinal view of a small specimen retaining both valves in conjunction. Doubtfully referred to 

 this .species. 



GlYPTOCARDIA 8PECI08A. 



Pago 426. 



See Plate 70. 



Pig. 10. View of a specimen retaining both valves, showing strongly developed surface ornaments, 



enlarged to four diametere. 



Byssopteria radiata. 



Page 25-2. 



See Plate 32. 

 Fig. 11. A large right valve. 



Chemung group. Mantfi^ld, Pa. 



Amnigenl^ Catskillensis. 



Pago 616. 

 See Plate 40. 

 Rg. 12. The right valve of a very large individual. 



Oneonta sandstone. Pennsylvania. 



