342 Prof. Bailey on Fossil and Recent Infusoria. 



forms of each determined, it will be easy to ascertain the true 

 position of any secondary or tertiary deposit from the examina- 

 tion of geological specimens not larger than mustard seed, and 

 which to the naked eye would offer no trace of organic remains. 

 4th. Microscopic bivalve crustaceans, resembling Cypris in 

 form but of marine origin, are very abundant in many of our 

 tertiary deposits. 



EXPLANATION OF THE FIGURES IN THE PLATE. 



All the sketches which accompany this paper, except A, B, C, and 

 D, were drawn from nature by myself, by means of the camera lucida 

 eye-piece attached to Chevalier's microscope. Most of them are mere 

 outlines ; but it is believed they will assist a student of this difficult 

 subject. They are all drawn to the scale shown in fig. 32. Figs. A, 

 B, C, and D, are copied from a plate of Ehrenberg's in the Report of 

 the Berlin Academy for June, 1844. 



Fig. A. Heliopelta Leeuwenhoekii, Ehr. Fossil at Bermuda. 



Fig. B. Asterolampra Marylandica, Ehr. Fossil at Piscataway, Md. 



Fig. C. Syrabolophora Trinitatis, Ehr. Fossil at Piscataway, Md. 



Fig. D. Craspedodiscus elegans, Ehr. Fossil at Bermuda. 



Figs. 1, 2, 3, 4. End views of fossil infusoria allied to Terpsinoe ? 

 Oregon. 



Fig. 5. Side view of the same. Oregon. 



Fig. 6. New species of Surirella. Fossil at Oregon. 



Fig. 7. New species, a of Gallionella. Fossil at Oregon. 



Fig. 8. New species, ^ of Gallionella. Fossil at Oregon. 



Fig. 9. New species, y of Gallionella. Fossil at Oregon. 



Fig. 10. Small fossil Navicula ? Fossil at Oregon. 



Fig. 11. Sceptroneis Caduceus, Ehr. Fossil at Bermuda. 



Fig. 12. Mastogonia heptagonse .-' Ehr. Fossil at Bermuda. 



Fig. 13. Stephanogonia polygona, Ehr. Fossil at Bermuda. 



Fig. 14. Xanthiopyxis oblonga, Ehr. Fossil at Bermuda. 



Figs. 15, 16, 17. Peripteras .? Fossil at Bermuda. 



Fig. 18. Chsetoceros Bacillaria, Ehr. Fossil at Bermuda. 



Fig. 19. Chsetoceros Diploneis, Ehr., with the spines partly brokea 

 off. Fossil at Bermuda. 



These figures, 18 and 19, I believe are only different positions of 

 the same species, for which I would retain the name C. Diploneis, Ehr. 



Fig. 20. Denticella polymera, Ehr. Fossil at Bermuda. 



Fig. 21. Dictyocba Ponticulus, Ehr. Fossil at Bermuda. 



Fig. 22. Dictyocba Quadratum, Ehr. Fossil at Bermuda. 



Fig. 23. Triceraiium Solenoceros, Ehr. Fossil at Bermuda. 



