SIXTH, OR OXYNOTICERAN BRANCH. 217 
layer, which formed the partition above the keel, and above this again a succes- 
sion of finer layers; but these did not fill up the interior of the keel completely. 
A hollow portion or zone filled in the fossil with pyrites, occupied the outer 
half of the interior of the keel. My notes and sketches make no mention of any 
dark layer in these specimens. 
Oxynoticeras Simpsoni, Hyarr. 
Summ. Pl. XIII. Fig. 11. 
Amm. Simpsoni, Simps., Amm. York. Lias, p. 37. 
Amaltheus Simpsoni, Wrieut, Lias Amm., p. 892, pl. xlvil. fig. 4-7. 
Amm. oxynotus (pars), Dum., Etud. Pal. Bassin du Rhone, pl. xxxiii. fig. 1, 4? (mot fig. 2, 3, 5). 
Locality. — Whitby. 
This species is quite different in form, sutures, and the amount of involution, 
and it is better to hold it as distinct than to confuse it with oxynotum. 
It is admirably figured by Wright. The shell is considerably more tumid, the 
whorl thicker and stouter than in oxynofum, and this peculiarity is observable even 
in the young. The amount of involution is greater, and consequently the um- 
bilicus is smaller, than in that species. The margins of the sutures are much 
simpler, especially as regards the auxiliary lobes and saddles than in oxynotum. 
It is intermediate in all its characteristics between oaynotum and Lymense, and this 
is an additional reason for separating it from the former. 
If we are right, either this species or a form transitional to it is found in the 
basin of the Rhone. 
Oxynoticeras Lymense, Hyarr. 
Summ. Pl. XIII. Fig. 12. 
Amaltheus Lymensis, Wriaut, Lias Amm., pl. xlvi. fig. 1-3; pl. xlvii. fig. 1-3; pl. xlviii. fig. 1, 2. 
Amm. Semanni, Dum., Etud. Pal. Bassin du Rhone, p. 154, pl. xl., xliii. 
Amm. oxynotus, Havrr, Ceph. Norddstl. Alpen, pl. xiii. fig. 8, 4, 8, 9 (mot fig. 6, 7). 
Locality. — Lyme Regis. 
This is merely a more involute form of Oxyn. oxynotum, which deserves a sep- 
arate name on this account, but is closely related to that species. 
Oxynoticeras numismale, Hyarr. 
Amm. oxynotus numismalis, Quenst., Amm. Schwab. Jura, p. 289, pl. xxxvii. fig, 1-8, 6, 7 (not fig. 4, 5). 
Amailtheus Wiltshirei, Wricur, Lias Amm., pl. xlviii. fig. 3. 
Locality. — Boll. 
This species has, according to Quenstedt’s figures, young similar to the adults 
of oxynotum, and the adult has a hollow keel. This is lost in old age, the whorl 
becoming rounded as in Lotharingun. It seems to be an extremely geratologous 
form of the first subseries surviving in the Middle Lias. The sutures are oxynoti- 
ceran in outline, and confirm this view of the affinities of the species. 
Quenstedt considers it identical with Ozyn. Oppeli, which is, however, a stouter 
form at the same stages of growth. He also erroneously identifies it with Ozyn. 
28 
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