. 
~ 
Parr III. Secr. iii. § 1.] CRETACEOUS. 807 
Mesozoic tribes of the Ammonites and Belemnites. These organisms 
continue abundant up to the top of the Cretaceous system and then 
disappear from the geological record. Never was cephalopodous life 
so varied as in the Cretaceous period just before its decline. Besides 
the forms that survived from earlier periods, but which had under- 
gone important modifications, new types now appeared. Of these - 
Crioceras (Fig. 394) was an Ammonite with the coils of the shell not 
- contiguous. Scaphites and Ancyloceras have the last coil straightened 
and its end bent into a crozier-like shape (Fig. 395). Tozxoceras, as its 
name implies, is merely bent into a bow-like form. Hamites is a long 
tapering shell, bent round hook-wise upon itself. In Péychoceras the 
long tapering shell is bent once and the two parts are mutually ad- 
herent. Turrilites is a spirally coiled shel!, and Helicoceras resembles 
it, but has the coils not in contact.. Baculites is the simplest of all 
the forms, being a mere straight-chambered shell somewhat like the 
ancient Orthoceras. ‘These forms, in numerous species, are almost 




< 
Fic. 393.—Cretacrous LAMELLIBRANCHS (HIPPURITIDS). 
a, Hippurites organisans (Desm.) (nat. size); b, Caprotina ammonia (D’Orb.) (1). 
entirely confined to the Cretaceous system, at the summit of which 
they disappear. Another characteristically Cretaceous cephalopod 
is Belemnitella (Fig. 396), which occurs only in the higher parts 
of the system. 
Vertebrate remains have been obtained in some number from the 
Cretaceous rocks. Fish are represented by scattered teeth, scales, 
or bones, sometimes by more entire skeletons. The most frequent 
genera are Otodus, Lamna, Oxyrhina, Ptychodus, Hybodus, Pyenodus, 
Spherodus, and the earliest of the teleostean tribes, which include 
the vast majority of modern fishes—Hnchodus, Stratodus, Beryx, 
Syllemus, &c. 
Reptilian life has not been so abundantly preserved in the 
Cretaceous as in the Jurassic system, nor are the forms so yaried. 
In the European area the remains of Chelonians of several genera 
(Chelone, Protemys, Platemys) have been recovered. Deinosaurs are 
represented by the huge Iguanodon of the Weald (Fig. 397), and by 
the Jurassic Megalosaurus and Ceteosaurus, which still survived, 
