140 GENESIS OF THE ARIETIDZ. 
Cal. (Aigoe.) Johnston, as figured by Wihner, Mojsis. et Neum., Beitr., IV., 
Plate XVI. Fig. 6-9, and Neumayr, Unterster Lias, Plate IIL, show that the 
typical coarsely pilated form of the Central European province exists also in 
the Northeastern Alps, but has probably a more limited number of descend- 
ants in that fauna. A not infrequent but very interesting variation in this 
species is the /orus variety, also present in the Northeastern Alps, Neum., Ibid., 
Plate III., and Wihner, op. ci/., Plate XVI. Fig. 6. It is distinguished by a 
marked tendency to sudden increase in the size of the whorl by growth at a 
late nealogic stage. The next gradation in the subseries, as exhibited in the 
Northeastern Alps, is a species having a still quicker increase in bulk, as de- 
scribed by Wihner, Cal. (goc.) hadroptychum, \bid., Plate XVII. Fig. 1-3. 
The increase in the whorl takes place quite early, and the coarse fold-like 
pile and rather broad whorls indicate the next step in gradation to be, as 
pointed out by Wihner, the unnamed form figured on his Plate XVII., which 
leads, as also pointed out by the keen eyes of this author, into the remark- 
able Cul. (Atgoc.) mgromontanum given on Plate XXIV. The affinity is better 
shown by the young figured on Plate XXV. Fig. 2, which is very similar to 
the adult of the preceding species. This species has a distinct but broad keel 
in the adult, and slightly compressed whorls similar to those of Oa. proaries, and 
is a good example of morphological equivalence. Cal. Liasicum, as described and 
figured by Wiahner,’ evidently has compressed whorls, and is more closely allied 
to Cal. Johnstoni in all varieties than the same species in Central Europe. 
Cal. (Ariet.) Loki* has close relations to Liasicus of the Northeastern Alps, 
as pointed out by Wihner, and Cad. (Ariet.) Seebachi® is also an allied species. 
SECOND SUBSERIES. 
The whorl is subquadragonal in the adult. An obtuse keel is always present. 
Very shallow channels are developed, and the pile are prominent, straight, and 
in some species have slight genicule like those of Vermiceras. 
The sutures, with the exception of Cal. laqueum,’ have an abdominal lobe 
deeper than the superior laterals, but the superior and inferior lateral lobes 
are of nearly equal size and length, the superior lateral saddles broader, but of 
about the same depth as the inferior laterals, and the marginal lobes and saddles 
similar to those of Psid. planorbe. 
The young are similar to Qal. Johnston. The clinologic period has a sub- 
acute abdomen, but this becomes rounded in the last part of the senile stage. 
The lobes in this stage return to their younger or psiloceran proportions, the 
abdominal lobe becoming shallower and broader, the lateral lobes narrower and 
shorter, and the lateral saddles broader and shallower in proportion. 
1 Mojsis. et Neum., Beitr., VI. pl. xx. + lbids, Vv... pl. XVil. e dbids; Vi Dl. xoc 
4 Cal. laqueum seems to have an abdominal lobe shorter than the inferior lateral lobes, and in some 
specimens the sutures are similar to those of the first subseries. In other specimens they resemble more 
closely those of Psil. planorbe, and in still others they become similar to the sutures of Vermiceras. 
