HYATT ON THE TERTIARY SPECIES 



V. Lists of Fossils by Sections. 

 Old Pit, Section 5-6. 



Formation " a. " 

 Stratum " a," 1, and a. 



This, the lowest observed stratum, was explored in two places in the Old Pit 

 by means of holes sunk through the fish layers, c, to the dark Jura clay beneath. 

 At the lowest points fossils were carefully collected, which are figured on plate 1, 

 lines a-k, and k-l. Lines a-h include the varieties obtained during the first visit 

 to Steinheitn, in the first hole sunk to the Jura-clay level, and also those collected 

 during the second visit in a new hole at a short distance to the northward and stiU within 

 the limits of the Pit. Lines Ti-l, include a selection of the varieties obtained in the 

 lowest stratum during the reopening and reexamination of the first hole dug and 

 described above, in order to establish the fact that Planorhis trochiformis occurred in 

 the Old Pit associated at the lowest level with PI. Steinheimensis, var. aequiumhilicatus. 



The descriptions and plates show that the following species, with many intermediate 

 forms, were obtained from the lowest part of the deposit, in contact with the Jura or dark- 

 brown clay. 

 PI Steinheimensis, Y&x.aequi- PI steinTe£nsis- -Pi- "dis'SiZl"- 



umUlicatus. PI tenuis. PI. *2fo^'SZ% similar to var. 



PI. Steinheimensis. PI- discoideus. elegans Hilg. 



PI- "''fir"*- ■^^" discoideus, var. involu- PI. trochiformis. 



T>7 Kraussii tUS 



-Til. steinheimensis- ' 



Stratum a2, Old Pit. 



This consisted, like the first stratum, of a brownish colored, coarse sand, but was devoid 

 of clay, and contained also stones or small boulders. The following species were foimd, 

 and are figured on plate 1, lines m-p : 

 PI. Steinheimensis var. ae- PI. '"^H^T''- PI- discoideus. 



quiumbilicatUS. PI- SteirSmensls- PI- 'dScoiS*- 



PI. Steinheimensis. PI- tenuis. 



Stratum a3. Old Pit. 



This consisted of sand of a similar coarse quality and color to that of a2, but contained 

 no large stones. The fossils were as follows, and are figured on plate 2, line a, and line 6, 

 figs. 1-4. 

 PI. Steinheimensis, var. ae- PI- Steinheimensis. PI. tenuis. 



quiumbilicatUS. PI- steinS^isis- PI- discoideus. 



Summary of Formation " a." 



The geological characteristics of the lowest observed stratum in each of the two holes 

 sunk to the level of the bottom clay differed. In the first hole, at the base of Section 6, 

 it was almost entirely shell-sand, but in the second hole, at the base of Section 5, the sand 



