144 GENESIS OF THE ARIETIDA. 
Caloceras Nodotianum, Hvyarr. 
Plate I. Fig. 7-11 a. Summ. Pl. XI. Fig. 16. 
Amm. Nodotianus, D’Orx., Terr. Jurass. Ceph., p. 198, pl. xlvii. 
Locality. — Semur. 
I have never seen the original, but the species as identified in D’Or- 
bigny’s collection and at the Museum of Semur, and also in Boucault’s collection 
named after D’Orbigny’s types, has not a close resemblance to Oppel’s type of 
Nodotianum. This last is probably its morphological equivalent in the genus 
Arnioceras, since it has smooth young, and is otherwise similar to Arnioceras. 
A specimen in the Museum of Comparative Zovlogy, said to be from Semur, 
has a stouter form and straighter pile than any specimen I have seen else- 
where. It has in these characters and in general aspect resemblances with 
forms like Cal. proaries, var. latecarinalum, but the abdomen differs in not being 
so much flattened. 
The fine suite of specimens in the Museum at Semur shows that this species 
has several varieties. One resembles. the variety of Cal. tortile from Walden- 
burg. Another, at 128 mm. diameter, has the sides inclined and the abdomen 
narrow, but not yet entirely acute. Another, even at the small diameter of 
57 mm., has an abdomen acute, as is represented in D‘Orbigny’s figure. The 
septal digitations of this species are not so complicated as in Zvasicum or the 
torus variety of Johnston. The examination of the specimens in the Museum 
at Semur shows them to have been derived from Cul. carusense. The shells 
found in the Tuberculatus bed resemble the adults of this species until a late 
stage of growth. Plate I. Fig. 11, represents the full-grown adult, and Fig. 11 
a section of the last whorl with its broad abdomen; Fig. 7, a larger specimen ; 
Fig. 9, 10, the approach of old age in a fragment of a still larger specimen. 
In the section the abdomen is shown growing narrower on the last whorl. 
Caloceras raricostatum, Hyarr. 
Var. A. 
Plate VI. Fig. 15. 
Amm. raricostutus, D’Orx., Terr. Jurass. Ceph., p. 212, pl. liv. fig. 1, 2 (fig. 3, var. By: 
Amm. raricostatus, QuENsT., Amm. Schwab. Jura, pl. xxiii. fig. 22, 23; pl. xxiv. fig. 4-10 (other figs., var. B). 
Ariet, raricostatus, Wricut, Lias Amm., pl. vii. fig. 2-6 (pl. xxvi. fig. 5-14, var. B). 
Ophioceras Johnstoni, Hyarr, Bull. Mus. Comp. Zool., I., No. 5, p. 75. 
Localities. — Lyme Regis, Somerset, St. Thibault, Semur, Salins, Balingen, Boll, Willershausen in 
Hanover. 
The pile apparently begin abruptly, but they are really preceded by de- 
pressed folds hardly perceptible to the naked eye. The pile are very closely 
set at first, but begin to be more widely separated on the fifth or sixth whorl. 
On the third or fourth whorl there are over forty, while on the eighth whorl 
there are not over thirty. No other changes take place in them or in the 
