SUMMARY. 113 



lum become simpler with advancing age, and more like those of planorbe, and by 

 the scarcity of the latter, which, though found by Wahner, 1 is declared to be rare. 

 One of Wahner's specimens was transitional to Hagenoivi in its sutures, and this 

 indicates that the province of the Northeastern Alps was the autochthonous 

 home of caliphjllum, planorbe, and Hagenoivi, and adds greatly to the probabilities 

 in favor of Neumayr's hypothesis. In Cal. Liasicum, Johnstoni, and nodotianum it 

 is common to find varieties varying in the sutures between the Mediterranean 

 and Central European extremes of modification, the latter being of course the 

 most numerous in their own province and rare in the Northeastern Alps. The 

 sutures of Liasicum? iortilis, 3 and nodotianusf when contrasted with Quenstedt's, 

 Wright's, and our own figures, give a good idea of the extent of variation, which 

 is quite as great as in Psil. planorbe, if not greater. 



Undoubtedly these facts, and the nearer approximation in aspect and sutures 

 of the Mediterranean forms of Psiloceras to Gymnites of the Trias, the genus we 

 have always regarded as the probable ancestor of the former, are strongly in 

 favor of Neumayr's opinion that the. forms of the European province arose by 

 chorological migration from the apparently more ancient fauna of the Mediter- 

 ranean province. The richer evolution of triassic forms in the Mediterranean 

 province, as described and illustrated by Mojsisovics, can also be brought forward 

 in favor of this view. Nevertheless, it is not right to yield entirely to the fasci- 

 nations of this opinion until there is positive proof that Psil. planorbe or caUphyllum 

 occurred earlier in this province than in Central Europe. 



With regard to the origin of Caloceras from this province, the facts are still 

 stronger in favor of Neumayr's view, but Vermiceras appears to have arisen in 

 South Germany. 



With regard to the origin of Wsehneroceras and Schlotheimia, it seems prob- 

 able from the zoological evidence that they also arose in the Mediterranean prov- 

 ince. The evidence is, however, geologically incomplete, since it is probable 

 that Schlot. catenata occurred quite as early in South Germany. Washneroceras, 

 the series of connecting forms uniting Schlotheimia and Psiloceras in this same 

 province, is not yet proved to be of as ancient origin as Schlotheimia itself, and 

 this introduces an anachronism which requires additional facts for its explanation. 



Mosch 5 has decided that the Lias to the west of the head-waters of the Rhine 

 contains species peculiar to the Central European province. W. A. Ooster's 

 descriptions and figures of species confirm this conclusion, since he does not men- 

 tion any novel species, though he describes twenty-one forms, representing more 

 or less all the genera of the Arietidas. 6 



Zittel 7 remarks that there is great resemblance between the Upper Lias in 

 Provence and Lombardy. Mojsisovics, 8 in quoting these observations, says that 



1 Verh. k. k. geol. Reiehsans., 1886, p. 169. 



2 D'Orb., Terr. Jurass., I. pi. xlviii. s Ibid., pi. xlix. * Ibid., pi. xlvii. 



5 D. Jura Alpen d. Ost-Schweiz, 1S72, p. 1. 



6 Cat. des Ceph. des Alpes Suisses, Denk. sehweiz. Gesellsch. Naturwis., XVIII., 1861 ; see also Studer, 

 Geol. d. Sehweiz, II. p. 231, for similar views. 



7 Central- Appenn., Geogn. pal. Beitr., Beneke, II. p. 174. 



8 Dolomit Riffe Siid-Tyr. uud Venet., p. 26. 



15 



