48 HYATT ON THE TERTIARY SPECIES 



If Avo assume in accordance with the contained fossils, that these layers belong to the 

 Trochi/oniiis zone, tlie difficulties become greater instead of less, as we shall see 

 farther on. 



Dr. Ililgendorf in his connminication " Neue Forschung in Steinheim," Zeitsch. d. 

 Deutsch. geol. Gesellsch., 1(S77, p. 450, writes that he tried to find during his 

 reexamination of all these hx^alities, single specimens of the higher varieties in the lower 

 strata, but without success, and also that no less than five other competent observers 

 failed in the same f(uest. This is very strong evidence, especially when taken in 

 connection with the tact, that Dr. Ililgendorf, with a, zeal which nuist make every 

 one desire to agree with him, sunk no less than ten holes to the Jura, and took 

 ph(jtographs and sections, going over all his observations again and again six times, 

 with great care. Altogether the amount of time, trouble, and study he has expended 

 is very remarkable, and worthy of the highest success, which 1 most heartily wish for 

 him. 



But although my observations cannot compare with his in these I'espects, there 

 are certain ficts which even the great mass of evidence he is able to bring to bear 

 upon this subject, do not seem to make clear. 



My two sections 5 and G i-eached the bottom of the deposits at the places where they 

 were made. Whatever formations they represent, whether deposited in deep or shallow 

 water, rest upon the original bottom of the lake. The trochifonnis fossils are not only 

 the remains of fresh, but also of rolled shells. These were found at a greater depth 

 in Section 5 than in Section 6. Therefore, if bed a in Section G was the equivalent of Dr. 

 Hilgendorf 's Discoideus or Sulcatus bed, or even if a, 1 in Section 5, was so high, how was 

 it, that on three occasions, and two different places, I found PI. trochiformis there. 



Dr. Hilgendorf's Trochiformis bed unquestionably lies unmediately underneath m, 

 the Oxysto7mts bed, in all my sections, and, if a in my section is part of the 

 Trochifo?'m!s zone, then the Trochiformis bed would extend from m, to the Jura, 

 a greater thickness, and a larger number of beds than could be included in that 

 formation, and yet preserve the sequence of the forms as described by him, since under 

 this again must come five out of the ten zones described by him. 



His recent researches may possibly remove these doubts by showing how this can be 

 accounted for, but there still remain other facts. 



Unquestionable PI. oxystomus oecm'red in the New Pit, much lower than m, the 

 first true Oxystomus zone of the Old Pit and of the Cloister Pit, namely in h, Section 

 8, together with P. crescens,^ which also ought not to have occurred until the Oxystomus 

 zone was reached. PI. oxystomus also occurred in Section 6, in bed i again in company 

 with PL crescens. 



Another point in this connection is the occurrence in a, 3, of Section 4, in a formation 

 lower than a Section 6, and equivalent to a 2 in Section 5, of a specimen of PI. ''",""',!f,;'f ■ 

 This is such an intermediate form as is figured on pi. 4, fig. 2, which does not occur 

 until e is reached in the Old Pit, pi. 2, line e. This specimen was found when hunting 



' This species also occurred iny, before PI. oxystomus. 



