260 A. E. Ortmann — Climatic zones in Jurassic times. 



other hand, if the alleged transportation of the empty shells 

 of the Ammonites over the seas should be correct, we ought 

 to observe actually a world-wide distribution of the fossil 

 Ammonite-species, but this is hot the case. Some species 

 indeed are found in the same zone all over the European Jura, 

 and some of them are found even in extra-European localities, 

 but this fact can never be a proof of the universal distribution 

 of the Ammonites in general. On the contrary, most of the 

 species are found only in limited localities and almost every 

 locality has its peculiar species. Whoever is occupied in 

 determining the different species of Ammonites and is 

 familiar with the systematic diversity of this group, ought to 

 know the local restriction of most of the species.* 



Neumayr, on the contrary, is inclined to regard the Ammon- 

 ites as animals swimming on the surface of the sea, as belong- 

 ing to the pelagic fauna (see Erdgeschichte, 1890, p. 270). 

 It seems that he was not aware that this supposition is very 

 dangerous to his theory. I do not want to deny that the 

 possibility must be granted, that perhaps some species or 

 genera of Ammonites belonged to the pelagic fauna, as well as 

 that some of them lived perhaps in abyssal depths of the sea ; 

 but by the actual distribution of these fossils I am convinced 

 that by far the greatest number of Ammonites lived as 

 benthonic animals in the moderate depth of the littoral, and in 

 this point I agree with Walther (1. c. p. 515). But further I am 

 convinced that they lived even in these places where now their 

 shells are found in the fossil state. It may be that the empty 

 shells could be transported in the manner mentioned, but such 

 a transportation could not take place over large tracts of the 

 seas, and could not be the normal condition of things ; other- 

 wise the actual distribution of the species of Ammonites 

 would be entirely different. 



From the foregoing considerations we have to conclude that 

 the Ammonites can furnish us with sure evidence for the 

 existence of faunistic differences, as Neumayr has indicated. 



I have still to make some remarks on the Reef-corals 

 alluded to now and then by Neumayr. Contrary to the 

 Ammonites, he tries to abate the value of the proof given by 

 the Reef-corals in regard to the former climatic conditions. 

 Generally we are wont to conclude from the recent exclusive 

 distribution of the Reef-corals in the tropical seas, that the 

 fossil Reef-corals also lived in seas of a tropical climate. 

 iNeumayr, however, urges on several occasions that we have no 

 sufficient reason for so doing, since Reef-corals may have 



* Already Tornquist (Fragmente einer Oxford fauna von Mtaru.— Jahrb. Hamb. 

 Wiss. Anst. X. 2, 1893, p. 24) calls Waither's hypothesis an "incomprehensible" 



