160 Mr.J. Lycett on the Upper Lias of Gloucestershire. 
A. Jurensis. Fragments only in the higher beds. 
A. crassus (A. Raquinianus, D’Orb.). Evidently the same 
shell as in the lower zone of the Cynocephala-stage at Nails- 
worth and in the Upper Lias of Yorkshire. 
Ammonites Iiminstrensis, n. sp. 
In its general figure it is scarcely to be distinguished from 
Ammonites Humphriesianus ; the style of its ornamentation is 
also very similar to that of the latter species; there are, how- 
ever, some well-marked differences. In A. Humphriesianus the 
lateral coste form, with the dorsal, a curvature more or less 
marked ; in the Lias shell, the ribs pass from the suture straight 
over the sides and back. Usually two, but sometimes three, 
dorsal ribs unite with one lateral rb. In 4. Humphriesianus the 
number of dorsal ribs is somewhat greater; but the most con- 
spicuous distinction consists in the form of the dorsal ribs, which - 
in the Lias shell are much more narrow, elevated, and acute, so 
that there is a wide space left between each rib. In the young 
shell the lateral ribs are likewise much elevated and acute, so 
that they are little larger than the dorsal ribs; there is also 
some little distinction in the figure of the volutions, and conse- 
quently of the aperture, the portion near to the suture over- 
hanging the preceding volution more than in the Inferior Oolite 
shell. 
The septa consist of three large principal lobes, much pro- 
duced, and of two small accessory lobes. The dorsal lobe is 
much lengthened, with a single, terminal, very elongated and 
pointed digitation upon each side of the mesial line; there are 
two smaller lateral digitations ; all the digitations are indented. 
The superior lateral lobe has its termination trifurcate, the me- 
sial digitation being pointed, and of immense length ; but the lobe 
altogether is less lengthened than the dorsal lobe. The inferior 
lateral lobe is similar in figure to the superior lobe, but is much 
smaller and shorter. The two accessory lobes are very small and 
simple, the second being nearly concealed by the convexity near 
to the suture. The dorsal saddle is of great width, consisting 
of two principal divisions, of which the outer is much the larger ; 
each division has two principal branches with numerous inden- 
tures. The lateral saddle has two principal portions, of which 
the outer is the smaller; the mdentures are smaller and less 
conspicuous than in the dorsal saddle. The accessory saddles 
are small and simple, almost without indentures. 
Ill-preserved specimens occurred rather abundantly at Hol- 
comb, associated with A. bifrons and Astarte lurida. My 
friend Mr. Moore has favoured me with fine specimens from 
the pale-yellow bed of the Upper Lias at Ilminster, and smaller 
