OEGANIC DEPENDENCE AND DISEASE 



91 



In the later stages of the Devonian they seem less com- 

 mon and become increasingly so through the rest of Pal- 

 eozoic time. It would appear that the early Devonian was 

 the climacteric period of these Sabella-like boring worms. 



In seeking a designation for these tubes and burrows, 

 we have noted the fact that they were described by McCoy 

 under the name Vioa prisca from a Silurian moUusk, 

 Vioa being an existing genus of boring sponges, and as we 

 are convinced that such tubes as were indicated by McCoy 

 are referable to the worms, a more appropriate name is 

 required and we propose to apply to all of them the desig- 

 nation Paleosahella prisca (McCoy) disregarding differ- 

 ences in size, which are often obvious, and of curvature, 

 which are slight. We give abundant illustration of these 

 occurrences and in the explanations to them point out fea- 

 tures of special interest. 



Fig. 76. A stromatoporoid coral from the Niagara group (Silm-ian) of Hamilton, 

 Ont., with weathered holes of boring worms or sponges. 



