Horváth Géza (szerk.): A Magyar Természettudományi Múzeum évkönyve 16. (Budapest 1918)

Fejérváry, G.J.: Contributions to a Monography on fossil Varanidae and on Megalanidae 16

•(Csarnóta, Beremend). These combinations are naturally only based on the palaeogeographical and palaeontological data we presently dispose of, and material at hand is certainly not sufficient for elucidating the question in its details. The geographical distribution will moreover be yet discussed further on, palaeogeographical conditions being here only mentioned to prove that the latter, from a biological point of view, cannot have so far dissociated V. Hofmanni from V. marathonensis, as to oppose any objection to their being considered as one and the same species. Let us now go over to the other important factor of biological conditions represented by climate. As stated in competent literature

1 the climate which during the Miocene had been hot, d a m p and subtropical, gradually changed into Pliocene mediterranean climatic conditions. About German Miocene FRECH 2 writes as follows: «Das häufige Vorkommen von Palmenstänmren in der Braunkohle des Königreiches Sachsen, in Thüringen und bei Bonn deutet darauf hin, daß sich auch nördlich der erst in der folgenden Miocänzeit aufgewölbten Alpenkette ein subtropisches Klima wieder einstellte.» At the beginning of the Miocene therefore, according to KAYSER,

3 the climate was «recht warm und feucht» notwithstanding traces of the influence of frost having been established on certain fossil leaves originating from the lower Miocene, which phenomenon, in the course of the T e r t i a r y period, cannot however be considered as yet marking a refrigeration of the World's climatic-conditions in general.

4 Thus despite subtropical climate, V. Hofmanni may have been exposed to the influence of cooler weather in the lower Miocene already, — just as is the case with the recent V. griseus inhabiting still the temperate regions around the Caspian Sea. Succeeding the Miocene, the Pliocene mediterranean climate gradually cooling down (in Northern and Central Europe) advances towards the Glacial period. Neither can therefore the difference in temperature existing between the subtropical and médite r r a n e a n climate be considered — again referring to the example of the recent V. griseus — as a sufficient biological cause for the establishing, from that point o f vie w, a necessary postula tum of a variation between V. Hofmanni and V. marathonensis. In consequence of the tolerably uniform nourishment of Monitors the respective fauna coming into consideration can 1 KAYSEB, op. cit., 1915, p. 338; W. H. ECKARDT, PalaeTklimat.. Samml. GÖSCHEN, Nr. 482, L'ipzitr, 1910, p. 105-108. s Aus d. Vorzeit d. Erde, Bd. V, (Aus Nat. u. Gr-istesw., Nr. 211) Leipzig, 1911, p. 118. 3 1. c. * * ECKARDT, op. cit., p. 51—52.