i eae 
SUMMARY. Ly 
Alps, and thence they passed southerly into the Italian basin. Migrants also 
passed in all other directions into the residual basins to the north and south 
of the basins of the Céte d’Or and South Germany, in the province of Central 
Europe. 
While these faunas in the Northeastern Alps and Italy became analdainic 
faunas so far as the Arietidee were concerned, they were aldainic faunas for some 
other groups, like the Lytoceratide, and also very likely for the Liparoceratida, 
Deroceratid, and possibly other families. These mixed faunas, which have been 
deemed such sources of confusion, are in reality the most instructive, and will 
enable us to trace both chronological and chorological migrations with greater 
security, if the views here advanced are correct. 
Table V. shows that there are but two examples of what Neumayr calls cryp- 
togenous types in Central Europe, species appearing suddenly without apparent 
ancestors, Schiot. catenata and Psil. planorbe, var. leve. Schiot. catenata, however, 
cannot be called an unquestionable cryptogenous form in the Northeastern Alps. 
It is in that basin connected by intermediate forms, as stated above, with Psilo- 
ceras, and it is therefore probable that in course of time the geological evidences 
which are now confusing will be brought into accord with the paleozodlogy. 
Psil. planorbe is a radical derived from Psil. caliphyllum, or else from pre-existing 
triassic ancestors, and the absence of a complete series connecting it or Psi. 
caliphyllum with Gymnites of the Trias is evidently due to the absence of an 
equally complete series of formations. That the intermediate species might have 
been deep-sea forms, and therefore not represented in the rocky strata now 
exposed, as supposed by Neumayr, is an admissible explanation. Newberry’s 
hypothesis! of the retirement of the sea is, however, equally supposable, and has 
the additional recommendation of explaining the absence both of intermediate 
forms and of the sediments. Newberry thinks that the presence of intermediate 
links in paleozodlogic history, and their absence from localities so far explored, 
are explicable on the supposition that the chain of the rocky deposits is incom- 
plete in those localities, and that the sea had retired from them carrying with it 
the threads of life. The missing links of the record were then evolved in other 
places, but not brought back by the return of the ocean to its former shores. 
This seems to us more in accord with what is already known of the merely frag- 
mentary aspect of the geologic record in any one region, the occasional discov- 
ery of the absent leaves of the record in other places, and the want of absolute 
synchronism between the strata of Europe and those of America. 
That Psil. planorbe was a littoral form, as well as its congeners, can hardly be 
doubtful, since, besides the facts quoted above, they are found associated in the 
same series of layers with bones of saurians and even remains of insects in Eng- 
land. The remarks of Martin and other authors, quoted above, upon the charac- 
teristics of the lumachelle in the Céte d’Or, and the broken aspect of the shells 
of Ammonoids compared with those of swimmers like the Nautiloids, as stated 
by Terquem, in the department of Moselle, the opinions of Tate and Blake, and 
1 Circles of Deposition in American Sedementary Rocks, Proc. Am. Ass. Ady. Sci., XXII., 1878, 
pp. 185, 189. 
