176 GENESIS OF THE ARIETIDA. 
often have broad and gibbous whorls, like the young of sinemurtense, and the pile 
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 Reynés, from some representatives of 
which it cannot be distinguished. 
Coroniceras coronaries, Hyarr. 
Amm. coronaries, QuENst., Der Jura, p. 68, pl. vii. fig. 5; Amm. Schwab. Jura, pl. 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 
pile, divergent sides, and broad, elevated abdomen. The young with its large 
pile and prominent genicule 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 pila ; these last, having lost the genicule, 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,’ but the marginal lobes and saddles have degenerated more 
markedly. 
Coroniceras rotiforme, Hyarr. 
Plate III. Fig. 4-17b. 
Amm. rotiforme, Sow., Min. Conch., V. p. 76, pl. ccccliii. 
Amm. rotiforme, Zinv., Verst. Wiirt., p. 35, pl. xxvi. fig. 1. 
Amm. rotiforme, D’Ors., Terr. Jurass. Ceph., p. 293, pl. Ixxxix. fig. 1-3. 
Amm. rotiforme, Hauer, Ceph. Nordéstl. Alpen, pl. i. fig. 1, 2; pl. ii. fig. 7-9. 
Amm. rotiforme, Quenst., Amm. Schwab. Jura, pl. xv. ‘ 
Ariet. rotiforme, Wricut, Lias Amm., p. 278, pl. v. fig. 1-4; pl. vil. fig. 1 (not pl. ix. fig. 1-8). 
Localities. —Semur, Stuttgardt, Vaihingen, Balingen. 
Var. A. 
Plate ILI. 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 pile 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. 
aspen i, 
