176 GENESIS OF THE AKIETID/E. 



often have broad and gibbous whorls, like the young of sinemuriense, and the piloe 

 and sutures are also sometimes quite similar to those of that species. 



A specimen of this species occurs in the Scipionis bed of the collection at 

 Semur, in company with the Amm. Hehli of Reynes, from some representatives of 

 which it cannot be distinguished. 



Coroniceras coronaries, Hyatt. 



Amm. coronaries, Quenst., Der Jura, p. 68, pi. vii. fig. 5 ; Amm. Schwab. Jura, pi. xvi. 



Quenstedt's original is a very large cast, 470 mm. in diameter, and has about 

 thirteen whorls, with the young showing in the centre. It differs from variety A 

 of rotiforme in persistently maintaining throughout life the breadth and elevation 

 of the abdomen, together with the keel, channels, and ridges. 



The adult, though much larger, is similar to kridion in its heavy overhanging 

 pilae, divergent sides, and broad, elevated abdomen. The young with its large 

 pilae and prominent geniculaa is similar to the young of some varieties of rotiforme. 

 There is a broad space on either side of the abdomen, which even in Quenstedt's 

 large specimen is not covered by the succeeding whorl, a character also present, 

 though not invariable, in the adults of rotiforme and kridion. Quenstedt's figure 

 shows the undiminished dorso-abdominal diameter of the last whorl, and the effects 

 of senile degeneration in the pike ; these last, having lost the geniculse, thus be- 

 come reduced to massive bent folds. The form has been changed somewhat, 

 but nevertheless the keel, channels, and even the lateral ridges, are persistent. 



The sutures, though evidently senile, still have an abdominal lobe longer than 

 the superior laterals, 1 but the marginal lobes and saddles have degenerated more 

 markedly. 



Coroniceras rotiforme, Hyatt. 



Plate HI. Fig. 4-1 7 b. 



Amm. rotiforme, Sow., Min. Conch., V. p. 76, pi. ccccliii. 



Amm. rotiforme, Ziet., Verst. Wiirt., p. 35, pi. xxvi. fig. 1. 



Amm. rotiforme, D'Orb., Terr. Jurass. Ceph., p. 293, pi. lxxxix. fig. 1-3. 



Amm. rotiforme, Hauer, Ceph. Nordbstl. Alpen, pi. i. fig. 1, 2; pi. ii. fig. 7-9. 



Amm. rotiforme, Quenst., Amm. Schwab. Jura, pi. xv. 



Ariel, rotiforme, Wright, Lias Amm., p. 278, pi. v. fig. 1-4 ; pi. vii. fig. 1 (not pi. ix. fig. 1-3). 



Localities. — Semur, Stuttgardt, Vaihingen, Balingen. 

 Vak. A. 



Plate III. Fig. 4, 10, 14-16. 



This has smooth young during one or more, but rarely throughout two 

 volutions. Large, coarse approximated tubercles then appeared, and rapidly 

 developed into folds, which became more widely separated on the first quarter of 

 the third whorl, and acquired the aspect of the adult pike of Cor. kridion. The 

 keel appeared on the third quarter of the third whorl, but remained a mere 

 ridge, until the advent of the channels about one volution later, when it became 



1 In the adult stage the abdominal lobe was undoubtedly much longer in proportion. 



