FOURTH, OR CORONICERAN BRANCH. Heald 
well with those of datum, and lead us to hope that this may prove to be the adult. 
Certainly it is very distinct from the true Bucklandi, and the characteristics, so 
far as shown, are such as one might expect in the first senile stages of Cor. latum. 
Coroniceras Bucklandi, Hyarr. 
Plate III. Fig. 18. Summ. Pl. XII. Fig. 17. 
‘ 
Amm. Bucklandi, Sow., Min. Conch., II. p. 69, pl. exxx. 
Amm. Bucklandi, Zint., Verst. Wiirt., pl. xxvii. fig. 1. 
Amm. Bucklandi, Puwux., Geol..York., p. 1, pl. xiv. fig. 13. 
Ariet. Bucklandi, Wrieur, Lias. Amm., p. 269, pl. i. fig. 1-3. 
Amm. Bucklandi, Quensr., Amm, Schwab. Jura, pl. ix. fig. 1 (mot fig. 2, 3). 
Amm. Bucklandi costaries, QuENS’T., Ibid., pl. xi. fig. 1. 
Amm. solarium, QuENST., Ibid , pl. viii. fig. 1-3, 
Amm. sinemuriensis, D’OrB., Terr. Jurass. Ceph., p. 303, pl. xev. fig. 1. 
Amm. sinemuriensis, Quenst., Amm, Schwib. Jura, pl. xi. fig. 18-20. 
Cor. sinemuriense, Hyatt, Bull. Mus. Comp. Zodl., I., No. 5, p. 78. 
Localities. — Lyme Regis, Semur, Basle, Aargau, Scheppenstadt, Schaichhof, Balingen, Tiibingen. 
| 
| Var. sinemuriense. 
4 Plate III. Fig. 18. 
| : : 
This has young which closely resembles the young of Cor. datum. The breadth 
of the abdomen, divergent sides, immature folds, and tubercles are quite similar. 
| The folds also begin with large tubercles on the first part of the second whorl. 
On the third quarter of the third whorl the true pile begin. After this the 
abdomen no longer increases so fast in breadth, and finally, upon the latter part 
of this volution, or the beginning of the fourth, this region is hardly wider than 
a the dorsum, and the sides flattened. On the first or second quarter of the fourth 
whorl the pile become duplicate or triplicate, and the broad, thin, abdominally 
projecting tubercles characteristic of this species arise. These peculiar pile and 
tubercles occur, in some specimens, intercalated with single pilee and tuberculated 
genicule bending forward upon the abdomen. The keel on the third quarter of 
the third whorl was well developed, and must have appeared considerably earlier. 
The channels were but slightly developed on the first quarter of the fourth whorl, 
though they have well defined ridges, and probably began later than the keel, 
somewhere perhaps upon the last half of the third volution; but this could not be 
ascertained with certainty. One specimen from Semur had but two divided pile 
upon the third whorl; after this they remained single to the fifth volution, the 
last observed. D’Orbigny’s figure of Amm. sinemuriensis was taken from a young 
individual of about five and a half whorls, in which the pile are all divided. This 
is as exceptional in the species as are the specimens without any divided pilex. 
The superior lateral saddles are much narrower than the inferior laterals. 
The abdominal lobe is about one half longer than the superior laterals. 
A fine specimen of this species from Semur, Plate HI. Fig. 18, retains the 
peculiar characteristics of sizemuriense for five and a half volutions, with a similar 
rate of increase, and slightly divergent or flattened sides, These sides become 
then more rounded, the pile single, parting with their tubercles; and on the | 
eighth volution, or perhaps. sooner, the whorl assumes all the characteristics of i 
te 
