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EXPLANATION OF PLATE 15.
4. Transverse section of another Coprolite from Lyme, showing the internal foldings of the plate, with sections of scales of fishes embedded in it.
5. Exterior of a spiral Coprolite, from the Chalk Marl, near Lewes, showing folds and vascular impressions
analogous to those in No. 3.
6. Longitudinal section of another Coprolite, from the same Chalk Marl, showing the spiral manner in which the plate was folded round itself.
7. Exterior of another spiral Coprolite, from the Chalk at Lewes, showing vascular impressions on its surface, and the transverse fracture of the spiral fold at b.
In many other figures of Plate 15, a similar abrupt termination of the coiled plate is visible at b.
8. 9. Two other small species of spiral Coprolites in chalk; these as well as Figs. 5, 6, 7, are probably derived from fishes found with them in the chalk, near Lewes.
10, 11, 12. Coprolites from the Lias at Lyme, exhibiting well-defined characters of the spiral fold, with vascular impressions on their surface.
13. Similar appearances on a Coprolite found by Dr. Morton in the Greensand of Virginia.
14. Coprolite from the Lias at Lyme, bearing strong corrugations, the result of muscular pressure received from the intestines.
15. Transverse section, showing the abrupt termination of the folded plate in Fig. 14, and representing the flattened form of the spiral intestine.
16. Longitudinal section of the intestinal tube of a recent Shark, showing the spiral valve that winds round its interior, in the form of an Archimedes screw; a similar spiral disposition of the interior is found in intestines of Dog-Fishes, Figs. 1 and 2.
