CRETACEOUS PERIOD 
Conceals to-day : nor find they let or bar 
Till lands high raised in northern Canada 
Forbid advance ; and stay their being one 305 
With chilly waters of the Arctic zone. 
And in this mighty gulf, this central sea, 
That sweeps across a dozen States to be, 
Dwell forms of life that close resemblance bear 
To those that haunt the eastern hemisphere. 310 
Here live and die lime-forming rhizopods, 
Mussels and oysters in their scalps and beds : 
Sea-urchins, sponges, limpet, sea-snail swarms, 
And Ammonoids of old and later forms. 
Here too the cuttle Belemnites are thriving ; 315 
And " Lamp-shell " tribes, though not so prosperous, living. 
Fishes abound, but not such wealth is here 
Of form as in the eastern hemisphere. 
The gristly groups of ganoids, sharks, and rays, 
As in Europa's seas, pursue their ways ; 320 
But though the bone-framed fishes lag behind ; 
Yet some of these, and monsters of their kind, 
Are in the gulf. A form unknown to-day 
The Portheus called here seeks and slays his prey. 
Twelve feet is he in length ; voracious too 325 
As any shark or ray the ocean through. 
Here too the perch-like Beryx swims the tide, 
And forms to barracudas close allied 
89 
