142 GENESIS OF THE ARIETIDA, 
this species. The abdominal view is not similar, not being flat enough on the 
abdomen, but the lateral view has the straight perfect pile of this subseries. 
The Amm. Burgundice, Martin, as identified at Semur, is identical with this 
species. It is, however, smaller than those from Saulieu, which are associated 
with Psil. planorbe, and is placed in the same bed as Liasicum. Wiihner’s figures 
and description of Arie. Scylla,' Reynés, seem to agree closely with the descrip- 
tions and figures of this species, The aspect of the umbilical or young whorls 
in Wahner’s figures shows that Sceyl/a, Wih., is certainly not identical with 
the Johnstoni-like variety of Cal. raricostatum, though it very closely resembles 
that form. 
Caloceras carusense. 
Plate I. Fig. 15, 16. Plate II. 1-3a. Summ. Pl. XI. Fig. 15. 
Amm. carusensis, D’Oxs., Terr. Jurass, Ceph., pl. Ixxxiv. fig. 3-6. 
a 
Amm. Arietis, Zint., Verst. Wiirt., p. 3, pl. ii. fig. 4 (not fig. 2, 3). 
Amm. spiratissimum, Hauer, Ceph. Lias Nordéstl. Alpen, pl. iii. fig. 1-3.? 
Amm. latisulcatus longicella, Quenst., Amm. Schwab. Jura, pl. xii. fig. 5 (not fig. 1-4, 6). 
Amm. laqueus (pars), QUENST. 
Amm. Scylla (pars), Reynks, plates. 
Localities. — Lyme Regis, Semur, St. Thibault, Balingen, Willershausen in Hanover, Luxemburg. 
The characteristic of this species as given by D’Orbigny, the crossing of 
the abdomen by the pile, is not an important peculiarity, since it 1s com- 
mon in the young of caloceran forms. The young of the normal variety is, 
however, identical with D’Orbigny’s figure. It acquires the keel when the 
shell is about 25 mm. in diameter, and is at this stage very similar to one 
variety of Cal. laquewm. The sides in the later stage and adults become more 
flattened, and the abdomino-dorsal diameter of the whorl increases proportion- 
ally. One variety in the Museum of Comparative Zodlogy has much stouter 
more quadragonal whorls than this, with flattened sides and abdomen, though 
the pile are never very prominent or perfectly geniculated. 
The abdominal lobe is long, and much deeper than the superior laterals. 
This is owing largely to the non-development of the superior laterals, which 
remain short and broad. The superior lateral lobes are shallow and broad, the 
inferior laterals narrow, and not usually long in proportion. The most character- 
istic parts of the sutures are the first auxiliary saddles; these are remarkably 
large, and often tongue-shaped. The auxiliaries do not, therefore, incline back- 
wards, at least in adults. The marginal lobes and saddles, and the margins of 
the superior and inferior lateral saddles and lobes, are simple, and like those 
of Psil. planorbe. 
This variety retains the keel until a very late age, even after the shell 
becomes perfectly smooth. The form at this time is precisely similar to that 
of the old of the stouter variety of Cal. Nodotianum or tortile ; subsequently, how- 
ever, the whorl becomes round, as in Plate Il. Fig. 1-3a. This stout variety 
1 Mojsis. et Neum., Beitr., VI. pl. xxv. 
2 The specimen in Oppel’s collection enabled me to quote this as.a synonym. 
sie els ents is RSS sine STE is 8 
