BELEMNITES AND AMMONITES 75 
rocks. Newer types are found in Permian strata, 
and species occur in open-sea deposits of Triassic 
age in wonderful abundance. These deposits are 
found on the Pacific coasts of North America, also 
in the Eastern Alps and Western Thibet. The 
Cephalopods seem to have increased and flourished 
until the Cretaceous Period, in whose rocks the fossil 
Belemnites elongatus. Belemnites hastatus. 
Fig. 24.—BELEMNITES, INCORRECTLY CALLED “‘ THUNDER- 
BOLTS.”’ 
remains are numerous and greatly varied. After 
that period their vitality seems to have ebbed, and 
many forms became extinct. 
The two forms of Cephalopods known as Belem- 
nites and Ammonites may have been brought to your 
notice already. J remember being greatly interested 
in them when I was a small boy. Belemnites were 
commonly found among the gravels with which 
