96 HYATT ON THE TERTIARY SPECIES 



Dr. Hilgendorf in his last exploration, however, has repaired this omission. He found 

 that the base of the section rested upon Opalinus clay, an older formation of the Jura 

 than those which are at the bases of the other sections. He also ascertained that the 

 lowest beds contained only PI. Steinheimefisis, a fact of the greatest importance to his 

 theory. This, however, does not seem to me to be conclusive, even though confirmed 

 in other sections, for reasons given elsewhere. In fact, the occurrence of the true 

 PI. Steinheimensis bed in these elevated deposits makes it very difficult to account for 

 the absence of this bed in lower situations, such as those represented by Sections 5, 6. 



Formation "k," Cloister Pit. 



This consists of shell-sand and contains the following fossils in the lower part : — PI. dis- 

 coideus, PI. minutus. PI. discoideus was the only fossil Planorbis found in the upper 

 part. 



Plate 3, line c, figs. 17-19, and line d. 



Formation "1," Cloister Pit. 



Consists of layers of shell-sand, with the usual limestone partings, and contains 

 -PZ- '^f^lr ^ pci'i'vus (pars). PI. crescens, PI. ""^S?"* var. revertens, PI. oxystomus, PI. oxys- 

 tomus var. cochleatot, PI. supremus var. turrita, PI. supremus, PI. discoideus, PI. *'diJ^fSl% 

 PI. trochiformis. 



Plate 3, lines e-7c, and lii].e I, figs. 1-14. 



Formation "m," Cloister Pit. 



This is like " ?," lithologically, and contains: — PI. "^^^f^™"' yslv. revertens, PI. oxys- 

 tomus, PI. supremus var. turrita, PL discoideus, PI. trochiformis. 

 Plate 3, line I, figs. 15-17, and lines m-p. 



Formation "n, o," Cloister Pit. 

 This consisted of sand layers with limestone partings like formation m, but contained 

 no fossils. Above this occurred a bed of rubble consisting of disintegrated rock, appar- 

 ently derived from the Cloister-ridge rocks and resembling in character that previously 

 encountered on the north slope of the hill, but containing no fossils. 



