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Sa 
60 GENESIS OF THE ARIETIDZ. 
Cal. nodotianum, as found at Semur, has two varieties. One of these resembles 
the subquadragonal varieties of Cad. carusense until a late stage of development 
with somewhat flattened sides, similar pile, keel, and faint channels. Afterwards 
it assumed the more acute form of whorl characteristic of its own species. Cal. 
sulcaum®* is transitional to Cal. Deffneri in its characters, but is not very closely 
allied. The sutures of Deffneri and its young form as seen from the side 
appear to justify the position given it as the extreme form of the caloceran 
series. In the Mediterranean province Cal. Johnstow’ also occurs, and exhibits 
transitional characters similar to those of the same species in Central Europe. 
The pile are coarse, like those of the young in Psiloceras, and there is the same 
tendency to an elevation of the abdomen, as in the same species in Central 
Europe. Our remarks upon the subseries of this genus in the Northeastern 
Alps are open to the objection that they were made upon the drawings of Neu- 
mayr and Wiahner, but our inferences do not differ widely from those of either 
of these writers, except in the names given to the genera and in the rejection of 
the name Arietites. We shall sufficiently discuss the details of the subseries 
occurring in the Northeastern Alps under the heading “ Caloceras,” in the chap- 
ter on “ Descriptions of Genera and Species,” and shall find that these in part 
exist also in Western Europe. 
The first subseries in the Northeastern Alps contains the well known Cui. 
Johustom. This seems to be the immediate radical of a small series, consisting of 
Cal. hadroptychum, an unnamed form also figured by Wihner, and the giant Cal. 
mgromonatum. The last has a keel, but no channels. ; 
This subseries also includes Oa/. Liasicum, which is very close to Cal. Johnstoni, 
Loki, and Seebachi, species having very immature keels, shallow channels, and 
slightly depressed abdomens connecting Ziasiewm with Cul. Haueri of the next 
subseries. 
The second subseries includes forms like Cul. proaries, which shows in its 
development how closely they are all connected with Psiloceras and the forms 
of the first subseries. This is the representative of Cal. nodotianum of Central 
Europe, and a close ally of this species, though the young are apparently more 
immature at the same age in the development of the keel and form of whorl. 
Cal. gonioplychum appears to connect this with the extraordinary series of Cal. 
cycloides, Doetzkirchneri, Castagnola’, and abnormilobatum. This is peculiar to the 
Mediterranean province, and shows that, like Psiloceras in the same region, Calo- 
ceras probably had a complete cycle of forms, varying from the discoidal psiloce- 
ratitic transitions with more or less elevated abdomens resembling Cal. Johnstoni 
and tortile to Cal. abnormilobatum, having complicated sutures, more involute, com- 
pressed whorls, and a narrowed umbilicus. This series, however, though it 
evolved an elevated acute keel in the two highest species, did not have deep 
channels in any species. 
This subseries also contains Cal. daqueum, var. scylla, and Cal. prespiratissinum, 
two forms that approximate to Vermiceras in their characteristics. 
The third subseries arose apparently from Cal. Loki or Seebachi. The young 
1 Summi. Pl. xi fig, 16. A Sumi. Pl. Si fig. 20121, 
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