Fig. 86. One valve of the pliyllopod crustacean Echinocaris punctata with marks 

 of Clionolithes borings among the surface ornament. Hamilton group (Middle 



. Devonian). 



Fig. 87. Clionolithes reptans; diffuse tu-bules in the shell substance of the brachio- 

 pod Leptostrophia. x 20. Oriskany (Lower Devonian). 



Fig. 88. The pygidium of the trilobite Homalonotns Belaiii exposing by weather- 

 ing the tubules of a similar species; natural size. Hamilton group (Middle 

 Devonian). 



