148 GENESIS OF THE ARIETID/E. 



cycloides, Wiih., 1 is a slightly more compressed form, which may be transitional 

 between the last and the next species, Gal. (Arid.) Doetzkirchneri. This last is 

 figured by Neuraayr. 2 Wahner's figures of the young of this species show the 

 rounded sides, slight keel, and pilaa similar to those which proaries has at later 

 stages in some specimens, and even in adult stages in others. Cal. (Arid.) Cas- 

 tagnolai, figured by Wanner, 3 shows in its very compressed whorls, narrower 

 umbilici, and sharp prominent keel, which are well developed at an early stage, 

 when the shell is about 15 mm. in diameter, that the cycle of normal modifications 

 is approaching completion. Cal. (Arid.) abnormUobatum* gives us the final grada- 

 tion. This is a shell having still more compressed whorls, narrower umbilici, due 

 to the more involute whorls, and a more attenuated keel. 



This keel and that of Castagnolai leads to the suspicion that it may be hollow, 

 but Wahner is too keen an observer, as shown in his complete descriptions, to have 

 let such an obvious peculiarity pass unnoticed. His remarks also show that he 

 knows how to distinguish between the morphological equivalence of this sjiecies 

 with Oxynoticeras and its true genetic affinities, as demonstrated by the nea- 

 logic stages and their similarities to the later stages and adults of Castagnolai and 

 cycloides. Wahner's descriptions, which we did not consult until we had written 

 the above, are sustained by our experience so far as the serial relations and affini- 

 ties of Doet-Jdrchncri, cycloides, Castagnolai, and abnormilobaUim are concerned. 5 



Third Sub-series. 



This subseries contains species which have better defined channels and more 

 prominent keels in the adults than is common in the second series, and during 

 the clinologic stage these are still retained. The whorl in other words becomes 

 rounded only in the nostologic stages, and probably very rarely attains this ex- 

 treme of modification. The clinologic stage has also slightly flattened and 

 inclined sides. 



Caloceras sulcatum, Hyatt. 



Plate I. Fig. 19, 80. Summ. PI. XI. Fig. 20. 



Amm. Conybeari, Ziet., Verst. AViirt., pp. 3, 35, pi. ii. fig. 4? 



A mm. Nodotianus, Hauer, Ceph. Lias Nordbstl. Alpen, pi. vi. fig. 4? 



Amm. Icridion, Quenst., Amm. Schwab. Jura, pi. ii. fig. 7 (not fig. 5, 6). 



Locality. — Semur. 



This species is precisely similar to Hauer's figure, except that the sutures are 

 more distinctly caloceran, having the line of auxiliaries inclined backwards. Our 

 specimens are also somewhat stouter, the abdomen broader, the channels deeper, 

 the genicular more prominent, but the pilae and general aspect of the shell are 

 exactly similar. 



1 Mojsis. et Neum., Beitr., V. pi. xxii.. xxiii. 



2 Abhandl. geol. Reichaans., VII. pi. v. fig. 1. 



8 Mojsis. et Neum., Beitr., V. pi. xxii., xxiii. •> Ibid., pi. xxviii. fig. 4-7. 



'• We have given outline figures on Summ. PI. xi. of Cal. cycloides, fig. 17, Castagnolai, fig. 18, and 

 abnormUobatum, f\s. 10. 



