38 HYATT ON THE TERTIARY SPECIES 



To the east of the road to Heidenheim and on the low ridge crossed by the road, I took 

 a sample of rock which I considered at the time to be identical with that occurring in the 

 East Pit ; the more massive character of the deposit struck me at the time, but being 

 influenced by the conclusions of former authors I did not pay much attention to the local- 

 ity. I supposed that it was nothing more than a fragment of the limestones from which I 

 had already collected in the East Pit, and took only one hand specimen, and that only as a 

 precautionary measure.-' This is to be regretted since its connection with the Sylvana 

 Limestone and the Cloisterberg rocks is very remarkable. The fossils show that the gradual 

 character of the transition from one fauna to the other cannot be safely denied. PI. 

 discoideiis is represented by a full array of varieties, but the flatter forms predominate 

 such as are figured on pi. 1, line e, fig. 10-12 ; like these also the young in the few 

 cases examined had the true discoidean character. The extreme varieties, the stout form 

 similar to fig. 19, line f, pi. 2, or the thin form shown in figs. 10, 11, line h, pi. 1, are rarer 

 than the normal forms, though the observer is very apt to think the latter very abundant 

 until a close examination is made. PI. tenuis was sought for, but not found. 



Two forms occurred which are probably the young of PL stdn^i^nsis^ but it is not pos- 

 sible to determine whether they were these or the young of PI. Steinheimensis. The 

 upper umbilicus was entirely wanting, and the whorls had the shape of PI. tenuis, but 

 without its angularity, or flatness on the lower side, or its narrow umbilicus. 



Besides these there occurs a specimen of Hyalina subnitens Miill., and Vitrina Suevica 

 Sand. Though casts, these are well enough preserved to give positive grounds for 

 their generic identification. The second of these two species is described by Sandberger^ as 

 occurring in the Sylvana Limestone, on the west side of the valley, and the first as in the 

 same formation at Moringen and Undorf. Both are very rare, and it is quite remarkable 

 that they should occur in a single hand specimen of this rock taken at random from the 

 first available point. Lymneus socialis of large size was very abundant. 



The exposures of rock on the southern side of the Cloisterberg ridge are divisible into 

 two portions. The lower part occupies the lower border of the ridge extending in places 

 nearly to the top. Its structure, though finer than the Coarse Limestone on the Burgstall, 

 is very similar, and it was evidently deposited under similar conditions. Both are evi- 

 dently the product of speedy deposition in waters saturated with lime, as shown by their 

 coarse, irregular, granular structure, and numerous cavities which have led l;o the frequent 

 description of the latter as tufaceous. 



I surveyed these rocks on every available occasion, and obtained many hand specimens 

 without, however, being able to determine with certainty either that thej'- were connected 

 with the rocks to the eastward of the Heidenheim road, or what were their upper 

 boundaries. All varieties of PI discoideus are abundant, except those with very deep 

 sulcations on the lower or umbilical side ; these are very rare, as are also the deep, thick- 

 whorled forms like those on pi. 2, line f, fig. 19. The prevalent variety is similar to 

 that described above, from the rocks" in the valley to the east of the Heidenheim road. 

 They differ, however, in the young, which is more immature in aspect and precisely 

 resembles in a large number of forms the adult of PI. tenuis. This is, therefore, 

 an intermediate variety and must be designated as PI. "St"'. Specimens of PI. steiXimensu, 



» I have called this the Valley Rock, to distinguish it from " Op. cit., p. 602. 



other formations. 



