PLATE XXXII. 
Mytilarca umbonata. 
Page 257. 
Figs. 1-4. The right, left, anterior and posterior views of an individual preserving both valves. The 
specimen has been slightly compressed laterally, giving an unnatural sharpness to the rostral 
portions. 
Chemung group. Ithaca, N. Y. 
Figs. 5, 6, 7. The posterior, anterior and right sides of a specimen. Fig. 6 shows what appears to be the 
pallial line terminating near the beak. 
Chemung group. Mansfield, Pa. 
Mytilarca Chemungensis. - 
Page 258. 
Fig. 8. A small right valve showing the striated ligamental area. . 
Chemung group. Philipsburg, Alleghany Co., N. Y. 
Fig. 9. A left valve with the beak partially broken away showing the small cardinal teeth. 
Chemung group. Rockville, Alleghany Co., N. Y. 
Fig. 10. The interior of a left valve from an impression in the shale, showing the striated hinge-area. 
Chemung group. Rockville, N. Y. 
Fig. 11. A small, broad right valve. 
Fig. 18. An impression of the margin of a larg-e left valve, showing the form of the hinge and its breadth as 
extending within the margin of the shell. 
Chemung group. Rockville, N. Y. 
Fig. 14. A very narrow and erect left valve showing also the striations of the hinge. 
Chemung group. East Randolph, N. Y. 
Mytilarca regularis. 
Page 260. 
Fig. 12. A left valve' showing the broad rounded form and straight erect beak. 
Chemung group. Leon Centre, Cattaraugus Co., N. Y. 
Mytilarca carinata. 
Fig. 
Fig. 
Figs. 
Fig. 
See Plate 38. 
15. A small left valve. 
Chemung group. Near Elmira, N. Y. 
16. A small right valve showing the form of the shell. 
Chemung group. Factoryville, Tioga Co., N. I r . 
17. 18. Two opposite valves showing some variation in the form of the shell. 
. Chemung group. Near Elmira, N. Y. 
19. An internal cast preserving impressions of the cardinal and lateral teeth and showing the striated 
ligamental area. 
Chemung group. Near Elmira, N. Y 
Mytilarca attenuata. 
Page 260. 
Fig. 20. A left valve showing the erect subcarinate form and attenuate beak. 
Chemung group. Elmira, N. Y. • 
Byssopteria radiata. 
Page 252. 
. See Plate 80. 
Fig. 21. A right valve imperfect at the beak, but showing the surface characters and angular anterior side. 
Fig. 22. An imperfect left valve which shows the general outline. The radii are not so distinctly duplicate 
as on the other specimen. 
Chemung group. Mansfield, Tioga Co., Pa. 
