PLATE XXV. 
Figs. 1-(3. Plastomenufi coninmnis, different iiuli vidiuils, two-thirds uatnral size. Page 50. 
Fig. 1. Typical speciuien ; a series of costal bones, whose positions are conjectural; a, an edge view of 
the second from the top ; h, inner portion of the left hyosternal. 
Fig. 2. A posterior costal bone of another individual; a, edge view. 
Fig. 3. A costal bone of a third individual. 
Fig. 4. Distal part of a costal bone of a small and perhaps immature individual; a, edge of the same. 
Fig. 5. Part of a costal bone of a specimen of var. I; a, edge view of the same. 
Fig. 6. Part of costal bone of a second individual of var. I; a, edge view. 
Fig. 7. End of costal bone of type-specimen of Plastomenus lachrymalk; a, the edge view; h, fragment 
of another costal of the same carapace, natural size. Page 51. 
Figs. 8-10. Broken costals of Plastomenus serialis, natural size ; page 51. 
Fig. 8. From one individual; 
Fig. 9. From a second ; and 
Figs. lO-lOa. From a third specimen. 
Fig. 11. Plastomenus muUifoveatus ; part of a costal bone, natural size. Page 49. 
Figs. 12-19. Plastomenusfraclus, fragments of one iudividual, natural size. Page 49. 
Figs. 12; 18. Proximal ends of costals. 
Figs. 13-16. Middle portions of costals. 
Fig. 17. Distal end of a costal. 
Fig. 19. Anterior moiety of a vertebral bone. 
Figs. 20-26. Fragments of two individuals of Plastomenus corrugatus, natural size. Pago 48. 
Fig. 20. Sternal bone, below; a, above. 
Figs. 21-26. Parts of one specimen. 
Figs. 21,26. From middles of costals. 
Figs. 22,23. Distal ends of costals. 
Fig. 24. Distal extremity of first or last costal. 
Fig. 25. Portion of left hjmsternal boue, from below ; a, from above. 
Figs. 27-31. Fragments of carapace of the Trionyx leptomitus, natural size. 
Figs. 27-28. Median parts of costal bones. 
Figs. 29-30. Distal parts of costal bones. 
Fkk 30rt. Section at fractured edge of No. 30. 
Fig. 31rt. Distal extremity of No. 30; fore end of the costal broken off. 
