40 
HAROLD’S DISCUSSIONS. 
monster in the shape of a baseball bat, often more 
than fifteen feet in length. This has a special name, 
orthoceratite (straight hook). The fossils separate 
easily at the articulations. A narrow tube or cord 
seems to pass through 
the body from head to 
tail. These animals 
were not only large but 
numerous, and may 
easily have been the 
monarchs of the seas. 
Another cephalopod 
was similar in form, 
except that its shell 
was coiled like that 
of the nautilus, whose 
beautiful ‘‘ chambered 
cell” has been so well 
described by Oliver 
Wendell Holmes in 
his poem “ The Nauti¬ 
lus.” 
In the latter part of 
the age small, quaint- 
lookingfishes appeared. 
They foreshadowed 
what the next age was 
to be. The abundance of animal life indicates that 
the seas abounded in vegetable growth. There were 
algae, and perhaps many other seaweeds, but as the 
early plants consisted mostly of soft tissues, they 
Fig. 20. —Orthocerus, a cephalopod 
(restored). The shell in the up¬ 
per part is cut away so as to 
show a vertical section. mus¬ 
cular tube (“ funnel ”) by which 
water is expelled from the man¬ 
tle chamber; C, air chambers ; 
S, siphuncle. In the back¬ 
ground is a Silurian cephalopod 
of the nautilus form, curved 
like a ram’s horn. 
