PSILOCERAS AND CALOCERAS. 91 
M. Collenot’ mentions Amm. Johnstoni, tortilis, laqueum, and Burgundie as oc- 
curring in the Planorbis horizon. The collections at Semur show that Planorbis 
was small, and evidently already losing ground, whereas the fine suites of calo- 
ceran fossils indicate at least that this series had suffered no loss by migration 
when compared with the fauna of South Germany. This collection is also 
arranged to show a bed similar to the Laqueum layer of Quenstedt, called by 
Collenot the “zone of Amm. Laasicus,” which contains only caloceran forms, and 
also Psil. longipontinum. Cal. laqgueum is smaller, and more like the German form 
when found in company with Liasicus.? A few dwarfed forms of Psi. planorbe, 
var. deve, have been found together at Saulieu, and at Beauregard there is a bed 
with large forms of Cal. Johnstom and tortile, accompanied by a larger form of Cal. 
Jaqueum than is usual in South Germany, and a small Psvd. planorbe, var. leve. The 
latter is in Boucault’s collection, Museum of Comparative Zodlogy, but not rep- 
resented at the time of my visit in the collections at the Museum of Semur. The 
researches of M. F. Cuvier* are important in this connection. He states that a 
separable Planorbis bed was found by him on the section of the railway between 
Arcy-sur-Cure and Guillon, and immediately above this a bed characterized by 
the presence of Cal. Lvasicum. Again, on page 177, he speaks of finding at 
Gravelles, near Saulieu, a bed containing Psil. planorbe and Cal. laqueum or Bur- 
gundie, and this agrees with Collenot’s observations. 
Dumortier* states that Psi/. planorbe occurs everywhere in the Planorbis bed 
of the basin of the Rhone in company with Cal. Johnstoni, though not an abun- 
dant fossil, and from a fragment in his possession infers that the former may in 
some cases have reached the great diameter of 220 mm. Quenstedt describes and 
figures a specimen of Psi/. planorbe, var. leve, from Provence,’ which he names Amm. 
psilonotus provincialis, Martin® designates the Planorbis bed in the region of the 
Cote d'Or as the “zone of Amm. Burgundie” (our Cal. laqueum). He considers 
that the beds of “lumachelle,” the Planorbis horizon, show evidences of having 
been deposited during a period of violent currents, ete. This is an important 
fact, since it indicates the littoral character of the deposits. 
Terquem,’ in the department of Moselle, writes that Ammonites are generally 
rarer and more often broken than Nautili in the Lower Lias, and enumerates 
only six species. Chapuis and Dewalque state ® that in Luxemburg the Planor- 
bis zone is not fossiliferous.? 
1 Description Géologique de l’ Auxois, p. 209. 
2 The remarks of M. Collenot on page 164 are very instructive, and confirm the impressions received 
from the collections at Semur. 
8 Notice Géologique, etce., Bull. Soc. de Semur, ser. 2, No. 8, 1886, pp. 170, 176. 
4 Etude Paléontologique du Bassin du Rhone, p. 28, pl. i. 
5 Amm. Schwab. Jura, pl. i. fig. 19. 
6 Pal. Strat. de l’Infra-Lias de la Céte d’Or, Mém. Soc. Géol. de France, VII. 
7 Infra-Lias Luxem., etce., Dept. Moselle, Mém. Soc. Géol. France, V. See also, for similar opinions, 
Collenot, Deser. Géol. de ’Aux., p. 162, and Dumortier, Etudes Pal. Bass. du Rhone, I. p. 20, II. p. 97. 
8 Descr. Foss. Terr. Secon. de Luxembourg. 
9 The late researches of Schumacher, Steinmann, and Van Werveke, Erlaut. z. Geol. Uebersichtsk. d. 
Westl. Deutsch-Lothringen, show that the Planorbis bed containing Psil. planorbe, var. plicatus, is found in 
the region explored by them, though it is absent in the French part of Lothringen, as stated by Bleicher, 
Bull. Soc. Géol. de France, ser. 8, XII., 1884, p. 445. In Deutsch-Lothringen it is one meter in thickness. 
