DANFORD : NOTES ON THE SPEETON AMMONITES. 105 
rib, seems to be rather the rule than the exception. In other 
respects this form seems to be of the Beani type. 
It has been thought that it was from this, and the pre- 
ceding beds, that the earher collectors obtained their fine ex- 
amples of the " coronated " Ammonites ; but the phosphatic 
condition of most of their specimens, and especially of the 
splendid series in the Leckenby collection at Cambridge, points 
to these fossils having come from the base of the succeeding 
bed, D2, and not from D3 and D4, where, as far as my experience 
extends, the Polyptychites are, when at all well preserved, always 
in the pyritous state. 
This bed, D2, which averages only about 2J feet in thick- 
ness, is perhaps the most interesting of the entire series. It 
is formed of dark gritty clays, easily distinguishable from the 
yeUowish-brown deposits of D3. In its upper three-fourths 
there are not many fossils, but the half-dozen inches of its very 
compact base is crowded with them, as well as with phosphatic 
stones, " potato nodules," and larger concretions. Most of 
the phosphatic lumps are partly rounded and pitted, partly 
flat or angular, as if the masses to which they originally belonged 
had after long exposure broken up, and their fragments had 
soon been covered by sediments. Indications are not wanting 
that some, if not most of them, are derived from Ammonite 
casts. The nodules, soft and brown outside, hard and dark 
within, do not enclose fossils, though Belemnites, and very 
rarely Ammonites, are found adhering to their softer exteriors. 
The concretions consist of these lumps, nodules, and a variety 
of fossils, often in widely different states of preservation, cemented 
together by pyritous materials. Ammonites both square and 
round-backed are here numerous, the former represented by 
H. regalis, H. hystrix, &c., the latter by a larger number both 
of species and individuals. Some of the small forms are well 
preserved in the ordinary condition ; others, small and large, 
round and square-backed, are more or less crushed, mere soft 
clay casts, or much impregnated and encrusted wdth pyrites, 
while many are in a phosphatic state, hard, dark, and 
brittle. 
