Hyatt.] 
22 
[May 16, 
Neumayer and Wahner have shown the ancient character of the 
fauna of thePlanorbis and Angulatus beds of the Lower Lias in the 
basin of the Northeastern Alps. The appearance in the same region 
of the very abundant fauna of the Trias, so admirably described 
by Mojsisovics in his “Mediterranean Trias Fauna,” makes it still 
more likely that the geological succession was more direct in this 
region than in any other . 1 
The richness of the faunas of the lowest beds of the Lower Lias 
in the basin of the Northeastern Alps so completely described and 
beautifully illustrated by Neumayer 2 and Wahner , 3 that they are 
models for imitation, has added a large number of radical species 
to those few formerly known in Central Europe but has not added 
correspondingly to the progressive series. Neumayer states , 4 that 
the radical species of Psil. planorbe had varieties in Northeast 
Alps approximating to some in Central Europe, though probably 
derived directly from Psil. caliphyllum a smooth species of Psil- 
oceras not found in Central Europe. I have had a similar expe- 
rience in studying the Psiloceratites of Central Europe, and also 
Cal. Johnstoni and other Caloceratites of the same fauna. In these 
species, varieties are found having more complicated sutures like 
those of the same species in the Lower Lias of the Northeast Alps. 
The shells of this fauna are very generally characterized by having 
more complicated sutures, the outlines of the lobes and saddles re- 
sembling the species common in the Trias, and quite distinct from 
the outlines of the sutures in the normal forms of the Arietidse of 
the Lias in Central Europe. 
The sutures of the normal forms of the Arietidse in Central Eu- 
rope, and of the species originating in that fauna, have, as a rule, 
simpler outlines and are evidently more or less degenerate. This 
fact accords with the theory that they were derived from Psil. plan- 
orbe. The sutures of the Arietidse are more like those of the young 
of Psiloceras than those of adults of the same species. The shells 
of this genus, and in fact all of the Ammonitinse, have more com- 
plicated sutures in the adult than in their own young. Neumayer 
has also stated that in old age of Psil. caliphyllum the sutures de- 
1 This remark has been sustained by the discovery by Clarke of a Triassie form, an 
Arcestes in the Rhaetic bed of the vicinity of Aachen-See (see Geol. Verhalt. d. Geg. 
nordw. v. Aachen-See, by W. B. Clarke, now of Johns Hopkins University). 
2 Unterst. Lias, Abh. k. k. geol. Reichsan., vol. 7. 
3 Mojsis., et Neum. Beitr. vols. 2, 3, 4, 5. 
4 See 12, p. 43. 
