— ne 
FOURTH, OR CORONICERAN BRANCH. 171 
The shell of variety A is smooth for three or three and a half volutions; the 
tubercles begin to spread entirely across the sides on the first quarter of the 
fifth whorl, and about this time the geniculee have become prominent. The chan- 
nels are not present in any of these specimens, but more or less faintly marked 
narrow depressed zones may be observed on either side of the keel. This variety 
leads directly into the next, in which the depressed zones become channels. The 
geniculs differ in aspect from those of variety A, because they abut against the 
well defined lateral ridges of the channels. 
Variety B has the pile developed at about the same period as in variety A, 
but the channels appear in the young, and on the second quarter of the fifth 
volution they are quite distinct. 
There is one specimen of variety A in which the pile are slightly inclined 
posteriorly, and the genicula more prominent than in any other specimen. A 
very slight sinking of the abdomen in this specimen would produce a form of 
variety C, which is found at Robin Hood’s Bay in England, and which has a 
keeled, channelled, and flattened abdomen. The single suture which was exposed 
in this specimen possessed remarkably pointed and serrated superior and inferior 
lateral saddles, and very broad, rounded, but serrated superior lateral lobes. The 
auxiliary saddles and lobes were pointed and serrated. There was a very large 
siphonal saddle, and all of the larger lobes and saddles appeared of about the 
same depth and length. 
One specimen of this species from Balingen was received in exchange from 
the Museum of Stuttgardt, under the name of Nodolianus. Two specimens in 
Quenstedt’s collection belonged undoubtedly to this species, variety A. One 
from Lias, a, Pforen, named Amm. falcaries (No. 4428), and one from Géppingen 
(No. 11182), were in the Arietenkalk. The last was 63 mm. in diameter and 
a typical form of variety A; the pile are, however, inclined posteriorly, while in 
the other they are pointed forwards. In the specimen from Pforen the pile begin 
abruptly near the abdominal side unpreceded by tubercles. Other specimens, 
especially the original of his figure, Plate VI. Fig. 6, also from Pforen, show 
that Hartmanni and this species have intermediate varieties. 
Several forms are found in the Semur collection under the name of Hettan- 
gensis, Rey., one of which has smooth young, with fine pilations and an adult 
whorl having close resemblances to this species and also to Arn. miserabile, var. 
acutedorsale. 
TuirD SUBSERIES. 
Arnioceras kridioides, Hyarr. 
Plate II. Fig. 28. Summ. Pl. XII. Fig. 8. 
Ophioceras kridioides, Hyatt, Bull. Mus. Comp. Zodl., I., No. 5, p. 75. 
Amm. kridion, Quenst., Der Jura, pl. vii. fig. 8, Amm, Schwab. Jura, pl. xi. fig. 5, 6 (not fig. 7). 
Amm. Bucklandi carinaries, Quenst., Amm. Schwab. Jura, pl. xi. fig. 3. 
Localities. — Basle, Semur. 
This species approximates in aspect to Cal. raricostatum, and was on this 
account at first erroneously referred to that species. The shell is, however, 
