90 GENESIS OF THE ARIET1D.E. 



they were probably taken from loose rock not in place, and may have come 

 from a dark gray limestone in the horizon of Psil. caMphyUum or megastoma. 

 They cannot, therefore, be considered forerunners of the psiloceran forms of 

 the Planorbis bed. 



Neumayr's and Warmer's researches, quoted below in Table VI. and in the 

 chapter on " Descriptions of Species," show that a wonderfully rich fauna of 

 Psiloceratites and Caloceratites existed in the region of the Northeastern Alps ; 

 but, so far as we know, there is nowhere any statement of the appearance in time 

 of the discoidal radical Psil. caliphyllum or planorbe before Caloceras in that prov- 

 ince, as there is in South Germany. The aspect of the fauna is older than that 

 of South Germany ; but though composed of an assemblage of radical forms of 

 Psiloceras, they occur side by side with Gal. Johnsloni and Schloi. catenata (subangu- 

 lare of Wahner), and are equivalent to the fauna of the Caloceras bed of South 

 Germany, but not to the lowest Planorbis bed. Suess and Mojsisovics, in their 

 table of strata in the mountains of the Osterhornes, 1 Northeastern Alps, describe 

 a very thick Planorbis horizon, and in the uppermost bed they enumerate Psil. 

 planorbe, supposed to be the English form ; also Psil. Hagenoui and Col. Johnsloni, 

 no fossils having been found in lower beds. Here again it is probably the 

 Caloceras bed, and not the lowest Planorbis bed, which contained the fossils 

 described. 



In South Germany Psiloceras p>lanorbe, the radical species of the Arietidse, is 

 prevalent, as may be seen in collections, and in the works of all the geological 

 writers on this region, especially Quenstedt. Quenstedt notes what he calls the 

 Laqueum layer, and speaks of caloceran forms as having made their first appear- 

 ance somewhat later in the Planorbis horizon than Planorbis itself, and in the 

 " Ammoniten der Schwabischen Jura " describes and figures a specimen, Planorbis, 

 var. leve, from the Bone-bed, which is placed by most writers in the Rhsetic. 



In the neighborhood of Salin and Besangon, Prof. Jules Marcou has shown 

 that there is a deficiency in the Planorbis horizon, and lately Louis Rollier, 2 

 following in his footsteps, has confirmed these observations. Professor Mar- 

 cou, however, at Boisset, near Salins, found a true Planorbis bed containing 

 the typical species. W. A. Ooster, in the " Catalogue des Cephalopodes des 

 Alpes Suisses," 3 enumerates many species ; but unluckily the beds are not de- 

 fined. It is, however, evident that the collections in Switzerland which he 

 examined, and the authors he quotes, did not give any data contradictory to 

 Waagen's conclusions, which we give below. 



Waagen, in his " Der Jura Franken, Schwaben und der Schweiz," says that 

 outside of Suabia, whether going northeast or southwest, one finds nowhere the 

 typical development of the Lower Lias as it exists in Suabia ; and it is especially 

 the lowest bed which is apt to be nearly everywhere starved out. This remark 

 and the table given by Waagen are very important, and coincide with the 

 results reached in this chapter. 



1 Gebirgesg. d. Osterh., Jahrb. geol. Reichsan., XVIII., 1868, p 195. 



2 Form. Jurass. Soo. d'Emulat. Porrentruy, 1883, p. 105. 

 8 Deuksch. schw. Gesellsch. Naturwissen., XVIII., 1861. 



