102 GENESIS OF THE ARIETIDA. 
which convinced me of the derivation of that species from Agassiceras, was found 
in 1875 in the Stuttgardt collection. The specimens of the last named species 
had been selected by Professor Fraas out of several barrels of specimens of the 
same species gathered in the same locality. I looked very carefully in all other 
collections, handling hundreds of specimens, without finding any duplicates of 
these forms. 
Hauer has given, in his ‘‘ Norddstlichen Alpen,” ! an involute form, apparently 
the same as Oxyn. Lymense, and figures of the young, which are, however, in part 
distinct.’ Tis Amm. G'reenoughii is evidently a member of the same subseries, and 
identical with the more involute forms of Amm. Giuibalianus of Reynés. This sub- 
series is only sparsely represented in the Northeastern Alps, and its date of 
appearance is not yet settled. 
The collection at Semur has this species in the Birchii or Tuberculatus bed. 
M. Collenot states that this bed in the Cote d’Or basin contains the same spe- 
cies and is equivalent to the Tuberculatus, Obtusus, Oxynotus, and Raricostatus 
beds of South Germany and England, and that it is not possible to separate the 
faunas, as has been done elsewhere. The appearance of the usual forms of Oxyn. 
oxynotum in great abundance in Southeastern France according to Dumortier, and 
also of Oxyn. Simpsoni and Lymense, shows that the last named forms may have 
made their first appearance in France. This is further substantiated by the fact 
that Oxyn. Lymense, according to Wright, is found more abundantly in the South 
of England than in the midland counties. The appearance of Oxyn. oxynotum 
and Lymense in the basin of the Northeastern Alps can be accounted for by cho- 
rological migration, in the same way that we have accounted for the presence of 
Asteroceras and others in that basin. The radical species, oxynotum, is cited by 
Schlénbach*® from only one locality in North Germany, and is not mentioned at 
all by Dr. Brauns in his “ Unterer Jura nérdwestlichen Deutschland,” or by 
Emerson. ’ 
The second subseries of this genus is completely represented in the fauna of 
France. Three species only are found in England, none in South Germany, and 
two in the Northeastern Alps. Apparently none have been found in North Ger- 
many* or Luxemburg. The collections at Semur contain a nearly complete 
series of forms, and Dumortier has added others occurring in the Rhone basin. 
The home of the series, therefore, appears to have been in the Céte d’Or or 
Rhone basin. 
This is the only series of the Arietidae which overstepped the boundaries of 
the Lower Lias. Other species have been reported by various authors as occur- 
ring in the Middle Lias, especially the Jamesoni bed; but these were found asso- 
1 Denkschrift. Acad. Wien, XI., pl. xiii. fig. 6, 7. 
2 Fig. 6, 7, appear to us to belong to some species of the second or Greenoughi subseries. 
8 Hisenst , etc., Zeitsch. deutsch. geolog. Gesellsch., XV., 1863, p. 502. Amm. affinis, however, de- 
scribed in Paleontogr., XIII. p. 170, pl. xxviii. III. fig. 1, by the same author, is from Middle Lias, Greene, 
Brunswick, which is very similar to if not identical with Oxyn. oxzynotum. We have not cited it in the 
table, however, since it may prove to be more nearly connected with Oxyn. Oppeli than with oxynotum. 
4 Schliiter describes Oxyn. Oppeli of the Middle Lias as occurring at Altenkirchen and Borlinghausen in 
the Teutoburger Wald, and Schlonbach describes and figures the same from Amberg. 
