150 GENESIS OF THE ARIETIDA. 
Caloceras ? Deffneri. 
Summ. Pl. XI. Fig. 21. 
Amm. Deffneri, Opr., Mittheilungen, II. p. 181, pl. xl. 
Locality, — Stuttgardt. 
This species has whorls at first sight apparently identical in form with those 
of the typical Conybeart. 
The young have prominent pile and geniculz on what seems to be the first 
quarter of the fourth whorl, and the genicula become tuberculated in the adult, 
without, however, exhibiting the angular forward bend of Conybeari. : 
The abdominal lobe is extremely broad, its lateral branches at first extending 
over the channel ridges on either side, and then diminishing to two pointed minor 
lobes. The siphonal saddle is very large. The superior lateral lobes are very 
narrow, profusely branching, a trifle longer than the abdominal lobe, and very 
much longer than the inferior laterals. These and the auxiliary lobes are often 
inclined posteriorly, as in Caloceras. The inferior lateral saddles are about as 
deep as the superior laterals, and have deeply cut margins, as in that genus. The 
first auxiliary, however, is often of considerable size, and then the inclined aspect 
of the inner margin is destroyed. The superior lateral saddles are penetrated by 
a very peculiar and remarkable marginal lobe, which divides them into two 
portions, the inner shorter than the outer half. The proportions of the lobes and 
saddles, and this last peculiarity, show, besides the form, a closer repetition of 
the characteristics of Conybeari than could have been anticipated from the gen- 
eral aspect of the shells. 
The channels are shallow, but have lateral ridges, and the keel is well formed 
and prominent, as in Conybeari. The series of this species in the Museum 
at Stuttgardt illustrates the different ages at which senile characteristics may 
begin to appear. The last specimen described above was only 175 mm. in 
diameter. Another specimen, however, reached the size of 380 mm., and yet 
only the last volution and a half exhibited senile degradation. The first senile 
half-volution had obsolescing pilze and tubercles, while the last half-volution was 
entirely smooth. The channels and keel remained almost unchanged, as in the 
adult. Not even a fragment of a living chamber was present. Oppel’s original 
is in the Museum at Stuttgardt. The eighth and ninth whorls of this speci- 
men are senile, the tubercles have disappeared, the sides are more convergent, 
and the abdomen more elevated than in the adult; the keel and channels, how- 
ever, were retained even after the pile disappeared, though they had become 
shallower. 
The sutures indicate affinity with the Caloceran series, but our knowledge of 
the early stages is incomplete, and this opinion is consequently uncertain. 
Neumayr in his “ Unterster Lias” figures a large specimen of Cul. (:Arvet.) 
Huueri, and gives a section. These show that the nealogic stages of this species 
are first similar to Johnston, then as the keel appears resemble Cul. Loki and the 
like, and finally take on the narrow channels of the adult. The closely set, bent, 
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