DAXFORD : NOTES ON THE SPEETON AMMONITES. 107 
situated about the middle of the flanks. These secondary 
ribs are very like those of Olc. (Simbirskites) umhonatus* 
Of two other forms I have also found but single examples. 
Both are Hoplites, one being somewhat of the H. oxygonius^ 
type, but with ribs that bifurcate with complete regularity 
unusually near the back. The branch, however, is often so 
much detached from the main rib that it presents an inter- 
mediate appearance. The other form is more compressed, 
with much finer ribs, which are regularly trifurcate about the 
middle of the flanks, the anterior being also generally detached. 
These forms have not yet been determined. 
The top of the zone, Dl, is well marked by the line of larg& 
nodules called by Mr. Lamplugh " the compound nodular band." 
They have mostly been formed round big Ammonites of the 
Hoplites type, and apparently sometimes Criocems, of which 
a large species is present in D2, but the fossils and the con- 
cretions are so worn that it is very difficult to distinguish 
species. 
These masses consist of bluish calcareous material, in which 
are embedded " potato " and darker nodules, which must have 
been formed earlier, but not much earlier, for the main 
and the subsidiary concretions contain the same fossils, among 
which are smaller and much better preserved examples of 
Hoplites regalis, Boubaudi and hystrix, Lateralis- and Jaculum- 
Belemnites, Bivalves, and Crustaceans as Myeria ornata, but 
never, I think, any of the Olcostzphani, unless some of the 
blacker lumps are fragments of their phosphatic casts. 
As the question at what horizon these latter Ammonites 
ceased to exist is of some interest, I have in the cliff carefully 
dissected a stretch of Beds Dl— D2, about 40 yards long by 
2 feet wide, and in this fairly large sample have not found 
a trace of the round-backed Ammonites above the basal six 
* Another specimen from the Comp. Nod. Band may be hetero- 
ptycktis, but seems nearer H. neocomiensis d'Orb. It is, however, too- 
fragmentary to be easily determined. 
