28 EXPLANATION OT PLATE 15. 



4. Transverse section of another Coprolite from Lyme, 



shewing the internal foldings of the plate, with sec- 

 tions of scales of fishes embedded in it. 



5. Exterior of a spiral Coprolite, from the Chalk Marl, 



near Lewes, shewing folds and vascular impressions 

 analogous to those in No. 3. 



6. Longitudinal section of another Coprolite, from the 



same Chalk Marl, shewing the spiral manner in 

 which the plate was folded round itself. 



7. Exterior of another spiral Coprolite, from the Chalk 



at Lewes, shewing vascular impressions on its sur- 

 face, and the transverse fracture of the spiral fold 

 atb. 



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 vas- 

 cular 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 cor- 

 rugations, the result of muscular pressure received 

 from the intestines. 



13. Transverse section, shewing 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, shewing 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, 



