FOURTH, OR CORONICERAN BRANCH. 169 
Arnioceras ceras, L. Acassiz. 
Plate Il. Fig. 20, 20a. 
Arnioceras ceras, L. Acassiz, Bull. Mus. Comp. Zodl., I., No. 5, p. 74. 
Amm. ceratitoides, QuENst., Amm. Schwab, Jura, pl. xiii. fig. 10 (not fig. 8, 9, 11). 
Amm. Turneri, Quenst., Ibid., pl. xix. fig. 6-8 (not fig. 5-9). 
Amm. ceras, HAvrr, Ceph. Lias Nordéstl. Alpen, p. 25, pl. vi. fig: 4-6. 
Localities. —Semur, Whitby, Lyme Regis. 
This species approximates to the aspect of Coroniceras, and also imitates 
closely the general form and characteristics of some varieties of Ast. Turneri. 
Both in England and Germany, when the interior of the umbilicus or the smooth 
compressed younger whorls are not preserved, even the most acute observers are 
apt to consider the adult whorl as belonging to Turneri. Some of Quenstedt’s 
figures, especially Fig. 8, Plate XIII., may be either ceras or some allied species 
of Armoceras. The keel is prominent, the channels are broader and deeper than 
usual, the genicule are prominent and slightly bent forward, the sides, however, 
flat and slightly convergent, and the pile straight and smooth, as usual in this 
genus. ‘The pile begin upon the third quarter of the fourth whorl. 
The superior lateral lobes are somewhat longer than the abdominal lobe. The 
inferior lateral saddles are one fourth deeper than the superior laterals, the infe- 
rior lateral lobes one half shorter than the superior laterals on the latter half of 
the sixth volution. 
A specimen in the Museum of Stuttgardt, locality uncertain, is referred to the 
Geometricus zone. Two young specimens from the Bucklandi zone, labelled 
Buckland (No. 2756), in Quenstedt’s collection, also probably belong to this 
species. The young are smooth, and the form differs from that of typical 
ceras only in being a trifle stouter. The channels, perhaps, also appear at quite 
an early period, but this sometimes occurs in specimens of the typical form. 
There is also a large specimen from Jettenburg. 
What appeared to be very close allies of this species were collected by Pro- 
fessor Orton at Ipishguaniina, in Northern Peru. 
Arnioceras Bodleyi, Hyarr. 
Plate II. Fig. 23-24a. Summ. Pl. XII. Fig. 7%. 
Amm. Bodleyi, Bruck., Murch. Geol. Cheltenh., pl. ii. fig: 
Amm. ceratitoides, QuENSt., Die Ceph., pl. xix. fig. 13 ; Amm. Schwab. Jura, pl. xiii. fig. 8, 9, 11. 
Amm. geometricus, OpreL (pars), Der Jura, Wiirt. Jahreshf., XI. p. 199. 
Ariet. semicostatum, Wriaut, Lias Amm., pl. i. fig. 4, 5, 8 (mot fig. 7). 
Arn. falearies, Hyatt, Bull. Mus. Comp. Zodl., I., No. 5, p. 74. 
Ariet. difformis, BuAxn, Yorkshire Lias, p. 289, pl. vi. fig. 3 a, b. 
Localities. — Whitby, Bonnert, Semur, Raidwangen, Basle, Salins. 
There are three varieties in this species; one, variety A, figured on Plate II. 
Fig. 23, has stout, thick whorls; the second, variety B, has flattened whorls; and 
the third, variety C, figured on Plate II. Fig. 24, has flattened whorls like those 
of the second variety, but they are somewhat wider on the sides. 
1 Proe. Bost. Soc. Nat. Hist., 1875, XVII: p. 366, 
99 
ca 
