124 GENESIS OF THE ARIETIDZ. 
planorbe. The saddles sometimes have entire margins, as in some Ceratitinee of 
the Trias. Neumayr’s Hagenowi, in his “Unterster Lias Nordalpen,”* is not a 
true Hagenowi, if the sutures are correctly drawn. Such facts and the remark 
of Wiihner quoted above (page 113) show that Hagenowi is probably a dwarted 
deformation of Psil. planorbe, which is likely to occur in any locality, and has an 
independent existence as a race or species only in certain basins where it is 
abundant. It seems to indicate, wherever it appears, that Ps¢/. planorbe has there 
been subject to unfavorable conditions. 
Neumayr in the work above quoted, Plate IV. Fig. 1, gives a Psil. (A/goc.) 
Naumann, a good-sized species with numerous folds, compressed slightly conver- 
gent sides, and a rounded smooth abdomen, exactly the form and characters of his 
Hagenowi, except that it is more decidedly plicated. The smaller Psi/. ( Aigoc.) 
erebrispirale, \bid., Plate V. Fig. 4, is probably the young of this shell. The sutures 
have complicated margins, as in pther shells of this province, and are not similar 
to those of Hagenowi. We place it here until its exact affinities can be settled 
by the study of a series, or of the young. 
Aigoceras Struckmanni? Vbid., Plate VI. Fig. 5, as remarked by this distinguished 
authority, is a unique survival of triassic forms. It resembles the flat-sided 
whorls in Tirolites, and even certain earlier forms, like Popanoceras. It may be 
provisionally associated with this series until the sutures are known, since the 
shell is smooth, and similar to that of Psé/. planorbe. This series should be care- 
fully studied with ample materials. It may be that confusion exists between 
some forms now supposed to be true Psil. Hagenowi and some triassic forms 
still surviving in the Lias. Canavari, in his “Fauna del Lias Inferiore di Spe- 
zia,” 1888, Plate VII., has figured a series of what appear to be true Tropites. 
These are very close congeneric forms of this triassic genus, and in our opinion 
should be referred to Tropites itself? This gives greater force to the suggestion 
made above. 
Canavari, in his “ Fauna des unteren Lias von Spezia,” gives some interesting 
forms of this genus. Psil. (dfgoc.), Plate XIX. Fig. 2, 4, 5, is a plicated form 
similar to pleuronotum. Psil. pleuronotum, Plate XIX. Fig. 3, may possibly be the 
same as Psil. caleimontanum, as stated by Wahner, but it is a dwarf, like most of 
the species from this locality. Pesil. (Aigoc.) Portisi, Plate XIX. Fig. 6, appears 
to bear a similar relation to Psil. mesogenos, Wéabner, however, considers it iden- 
tical with the young of his Psi. Kammerkurense. 
1 Abhandl. geol. Reichsans. Wien, VII. pl. ii.- 
2 Wihner’s Psil, Struckmanni, Unt. Lias, Mojsis. et Neum., Beitr., IV. p. 196. 
3 The survival of characteristic triassic forms in the Jura shows that the connections between these 
two systems are closer than has been supposed, and gives support to opinions advocated in the chapter on 
Geological and Faunal Relations, and adds another group to the three already noted, Psiloceras, Lytoceras, 
and Phylloceras. These facts demonstrate that no insuperable barrier arrested the migration of forms and 
the continuity of the faunas in time. See remarks on Tropites in note to page 154. 
4 Paleontogr., XXIX., and also Mem. del, Car. Geol. d’ Italia, III., 1888. 
eee 
