DANFORD : NOTES OX THE SPEETON AMMONITES. 109 
any higher seems doubtful. In CI, at the foot of Black CUff 
Ridge, it is common, but at that point the sequence of the 
beds along the shore is interrupted by a great landslip, and 
the condition of the ridge itseK makes investigation there 
difficult. 
Its near ally, H. oxygonius, with fewer and coarser ribs^ 
appears to have an equally extended range. H. amblygonius^ 
in which the ribs, also fewer, and coarser, form at the back 
an obtuse instead of an acute or right angle, as in the two pre- 
ceding species, chiefly occurs in the lower beds. H. Euthymi 
easily distinguished by its three rows of prominent tubercules- 
on each side, occupies a still lower position ; while H. hystrix, 
with similar tubercles, and coarse undulating ribs, which 
occasionally form loops between the tubercles, and H. Rouhaudiy 
with its regular arrangement of alternate simple and bifurcate 
ribs, appear to be confined to the immediate vicinity of the 
compound nodular band. 
Well-preserved specimens of this group are always of very 
moderate size, but remains, apparently of regalis and its nearest 
aUies in and near the compound nodular band, show that these 
Ammonites attained large dimensions, for many there measured 
were from one to two feet across. 
The Hoplites are not the only Ammonites of this zone^ 
for it is also tenanted by members of the Holcodiscus and 
Astieria sections of the Olcostephani. The former, represented 
by Olc. {Holcodiscus) rotula, is mainly met with in the lowest 
beds, and has been found by Mr. Lamplugh even in the compound 
nodular band. This species is not rare, and is sometimes rather 
large. The forms of the latter group, Olc. (Astieria) Astieri^ 
Atherstoni, spitiensis, and sulcosus, occupy a rather higher posi- 
tion ; such at least as I have found have not been near the base 
of the zone, certainly never in the Lateralis clays, where they 
have been said to occur, but usually near C9, the bed where 
the small nodules so often contain shrimps and other crusta- 
ceans, and which, owing to two distinct yellowish bands that 
run through it, forms a useful landmark in this often much 
