54 HYATT ON THE TERTIARY SPECIES 



iilarity which the upper layer of limestone in the pits presented, if the pieces were trans- 

 l^orted there, and thrown loosely together. 



It will, however be observed, that formation m, of the Cloister Pit, presents a fauna 

 closely similar to m, in the other pits, and that of n o above in all of the pits is 

 quite as similar to m, as the fauna of x 3, above is to that of x 1, 2, below, wherever 

 that bed occurs twice. There is, it seems to me, just the same reason for maintainino- 

 that m and n o are composed of drift, as there is for maintaining that x is made 

 up in this way. In conclusion, I would say also, that there are the most positive reasons 

 for the belief that x in Section 8, represents the upper and not the lower bed x, of Section 

 7. I find it so mentioned in my notes and sketches taken on the spot. I was, however, 

 unable to say whether m in Section 8 represented in alone, or both m and n o, 

 of Section 7, with absolute certainty, since the south-east corner of the pit was concealed 

 by a recent and heavy fall of loose materials. One thing, however, can be said with 

 certaint}^, that a bed corresponding to lower x, on the east side of the pit, as repre- 

 sented in Section 7, is not to be found on the south side, and the thickness of the clay 

 on that side is very nearly equal to that of the two clay beds on the east side, and 

 it has every appearance of being continuous with those two^ If, therefore, lower x is 

 drift, it had a very limited distribution, since it is certainly not found on the south side of 

 the New Pit. This also corresponds with the unquestionably mere pocket-like aspect of 

 the upper x deposit in the East Pit, and is evidently not in harmony with the supposition 

 that this is a bed of detrital matter, as represented by Dr. Hilgendorf, spreading over 

 the entire bottom of the lake. 



I do not consider this point of any great consequence, or worthy of much debate, 

 since it makes not the slightest difference with regard to the main question, whether PI. 

 trochiformis lived after the PI. oxystoimts bed was deposited, or not; though it is of vital 

 importance to determine whether oxystomus preceded trochiformis in time. 



One statement, however, of Dr. Hilgendorf 's is of great importance, since it shows that 

 very considerable changes likely to disturb the regularity of the deposits in very confined 

 areas, as is claimed here, did occur in one case, whether they occurred in the latest Trochi- 

 formis bed or not. On p. 452,^ he states that in the Sulcatus bed he found broken Stein- 

 heimensis clays " Platten," " tenuis Gesteinen," blocks of porous sulcatus tufa, clayey 

 sand and Jura pieces, all mixed in the greatest confusion, and two metres thick. This 

 mass evidently was of very limited extent and shows how great are the local peculiarities 

 likely to be found in any one spot from the transportation of material. 



As he says, these mixtures ai-e apt to escape a careless observer, and I might aild also, 

 any one pei'haps, not especially looking for them. In this extraordinary mixture, how- 

 ever, of the Sulcatus zone, he found no intermixture of the higher occurring forms. This 

 fact he justly regards as very important to his hypothesis, since the rocks also- are all 

 older than the stratum or zone in which he found them. 



The characteristics and situation of the bed I appear to make it very suitable as a 

 standard for the comparison of all the formations above and below its level. It occurs 

 immediately between the beds containing the trochiformis fauna, and those containing the 

 oxystomus fauna, and it affords a strong contrast in its fossils and lithological charactei's, 

 and is also apparently universal in its distribution. These reasons have induced me to 



' Nene Forscluing in Steinheim, Zeit. d. Deutscli. geolog. Gesellsch. 1877. 



