eg spot nm eetenneneeneanttineren 
FIFTH, OR AGASSICERAN BRANCH. 199 
gatus, maintains the aspect of sériaries until a late period of growth, and then 
develops the keel and form of Seipionianus ; and there is also another fossil, which 
is exactly similar to the later, but still immature, stages of Scipiomanus. 
The keel may, perhaps, have a hollow above the siphon, such as Quenstedt 
describes in his “ Ammoniten des Schwibischen Jura,” Plate XIV. Fig. 1, but 
the inner or nacreous layer does not form a partition between the interior of the 
shell and the interior of the keel, nor does the black layer occur above this par- 
tition, as in Oxyn. oxynotum and others, which have true hollow keels. In the 
specimens examined, the keel was elevated, as in Quenstedt’s figure, but the 
siphon laid directly against the shell layers, which filled the interior of the keel, 
and there was no black layer. 
Agassiceras nodosaries, Hyarr. 
Amm. nodosaries, QuEenst., Der Jura, p. 78, pl. viii. fig. 8; Amm. Schwib. Jura, I. pl. xvii. fig. 1-3. 
Locality. — Bempflingen. 
The specimen of this species in the Museum of Comparative Zodlogy is less 
compressed than those figured by Quenstedt, but it shows that nodosaries is prob- 
ably quite distinct from Seipronianus. The whorls are more compressed than in 
the latter, but the tubercles and pile are retained until a much later age. These 
same distinctions are, of course, still more marked when the species is compared 
with Seipionis. The exact horizon was not marked on our specimen. The 
cast measured 160 mm., and the outer whorl 60 mm., the same whorl at the 
beginning being somewhat less than 30 mm.; the greatest transverse diameter 
of the same was about 30 mm., and the least about 20 mm. Our specimen is, 
therefore, a trifle larger than the inner whorl of the fragment figured by Quen- 
stedt. in “ Ammoniten des Schwiibischen Jura,” Plate XVII. Fig. 1, at the point 
marked “k.” It is also of about the same diameter as his abdominal view of 
the same whorl marked “q.’ The keel is also in the same condition, being 
coated with matrix, the genicule are bent and run nearly to the keel, there are 
no channels, and on the younger part of this whorl the keel is well preserved and 
prominent. Quenstedt’s specimens were found in the Tuberculatus bed. It is 
not unlikely that the compressed variety of Agas. Scipionianum described above 
ought to be transferred to this species, but we have not been able to gather 
sufficient evidence to settle this question. 
Agassiceras Scipionis, Hyarr. 
Plate IX. Fig. 12,13. Summ. Pl. XIII. Fig. 8. 
Amm. Scipionis, Rrynis, Plates. e 
Amm. Scipionianus olifex, Quenst., Amm. Schwib. Jura, pl. xvii. fig. 7-10 (not pl. xv.). 
Locality. — Semur. 
The shell of this species is smooth at an early age, and quite similar to the 
old stages of Scipionianus in form and characteristics, but it is more involute. 
Quenstedt’s figures and descriptions of his Seipionianus ohfex appear to apply to 
