140 GENESIS OF THE ARIETID^. 



Cal. (JEffoc.) Johnstoni, as figured by Wanner, Mojsis. et Neum., Beitr., IV., 

 Plate XVI. Fig. 6-9, and Neumayr, Unterster Lias, Plate III., 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 torus variety, also present in the Northeastern Alps, Neum., Ibid., 

 Plate III., and Wahner, op. cit., 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 Wahner, Cul. [jEgoc.) Mdroptychum, Ibid., Plate XVIII. Fig. 1-3. 

 The increase in the whorl takes place quite early, and the coarse fold-like 

 pilae and rather broad whorls indicate the next step in gradation to be, as 

 pointed out by Wahner, 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. (YEffoc.) mc/romonlanum 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 Cal. proaries, and 

 is a good example of morphological equivalence. Cal. Liasicum, as described and 

 figured by Wahner, 1 evidently has compressed whorls, and is more closely allied 

 to Cal. Johnstoni in all varieties than the same species in Central Europe. 



Cal. (Aj-iet.) Lola 2 has close relations to Liasicvs of the Northeastern Alps, 

 as pointed out by Wahner, and Cal. [Ariel.) Scebachi 3 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 pila3 are prominent, straight, and 

 in some species have slight geniculse like those of Vermiceras. 



The sutures, with the exception of Cal. laqiiemn* 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 Psil. planorbe. 



The young are similar to Cal. Johnstoni. 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. pi. xx. 2 Ibid., V. pi. xvii. 3 Ibid., V. pi. xx. 



4 Cal. lanueum 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 o£ Psil. planorbe, and in still others they become similar to the sutures of Vermiceras. 



