21. Males also have more concave plastrons , believed to be another adaptation for mating. 22. The turtle's shell is divided into two sections : carapace and plastron . 23. The plastron is orange-red, and may also have large dark blotches. 24. The plastral scutes join along a central seam down the middle of the plastron . 25. The osteoderms of the carapace and plastron are smaller than those of other species. 26. They have an inflexible trunk encased in a horny carapace above and a plastron below. 27. A tracheal tube may contain ridge-like circumferential rings of taenidia in various plastron . 28. In many species, dimorphisms include elongated foreclaws or a concave plastron in the male. 29. The plastron also has bold colour pattern. 30. The plastron ( underside ) is yellowish.
