108 DANFORD : NOTES ON THE SPEETOX AMMONITES. 
inches of D2. The square-backed Hoplites, on the contrary, 
pervaded both beds, as did Lateralis- and Jaculum-Belemnites, 
the former showing a great decrease in numbers above 
the six inch Hmit, the latter an increase, sHght at first, 
but very marked in Dl. 
Shore exposures confirmed these observations, for though 
fragments of the round-backed forms sometimes occurred at 
the " compound nodular band," they were not in place, but 
had been washed in from the closely adjacent base of D2, 
and lodged among the large nodules. 
The development of the Belemnite and Ammonite immi- 
grants has here evidently been quite dissimilar, for the Jaculum- 
Belemnites, though found as low as D4, and even D5, do not 
attain their full strength until nearly the middle of the next 
zone C, whereas the Hoplites, which have not been met with 
below D2, are nowhere in greater force both as regards size 
and numbers than at the compound nodular band. 
Certainly the Jaculum-Belemnites on their arrival in the 
north must have found a vigorous, and perhaps hostile, crowd 
of their kinsfolk in possession. At all events they did not 
multiply much until the Lateralis tribe had vanished, but when 
the square-backed Ammonites came in from the south many 
of the round-backed species were probably extinct, and the rest 
may have been on the verge of extinction. Perhaps, however, 
it was all a matter of changed climatic conditions, which suited 
the one group better than the other. 
Zone C Jaculum Beds "). 
The most abundant Ammonite of this zone from Bed 7 
to its lowest bed 11 is Hoplites regalis* but whether it ranges 
* Prof. Pavlow points out that Neumaj^er and Uhlig have shown 
that the name Noricus, so generally applied to this Ammonite, is a mis- 
nomer, as the species is not fovmd near Xoris (Niirnberg), and that the 
name was originally given by Sehlotheim to an example of the genus 
Cosmoceras. 
