ORGANIC DEPENDENCE AND DISEASE 



87 



the Silurian as Vioa prisca and which was made by us to 

 include not only tubes of that type, that is, straight sub- 

 clavate fillings, but also very much smaller, much more 

 intricate, arborescent or vagrant tubules. It is evident to 

 us now that only the latter can be assigned to the sponges 

 and that hence our name Clionolithes, devised to suggest 

 relationship to sponges, is applicable only to this division. 

 It is proposed to retain the name for that group, even 

 though this may not be in precise accord with proper no- 



rig. 71. Etching of a tube cluster of Clionolithes radicans in the shell substance 

 of the brachiopod Leptostroplria magnified. From an enlarged photograph, x 64. 

 Grande Greve limestone (Lower Devonian). 



Fig. 72. The same in a shell of Atrypa reticuhtris from the Chemung sandstone 

 (Upper Devonian). 



