CHAP, X.| CONTINUITY OF THE CHALK. 483 
and he referred the group to the Polyzoa. When 
Mr. Toulmin Smith studied the Ventriculites, the 
Hexactinellida—the sponges with six-rayed meshes 
or spicules—were practically unknown, though there 
Fic. 80.—Ventriculites simplex, TouLMuin SmitH. Once and a half the natural size. 
were already a few examples in museums. One of the 
first results of deep-sea dredging was the discovery 
that the chalk-mud of the deep sea is in many places 
literally crowded with these; and when we compare 
Thee 
