ORGANIC DEPENDENCE AND DISEASE 



99 



-^jtwH».vwuaaf.. 



Fig. 84. Caulostreims taenioJa growing in the shell of the brachiopod Stropheo- 

 donta from the Coblentzian (Lower Devonian) of Seifen. The margins of the 

 brachiopod valves have been entered on all sides sim^iltaneonsly by these borers 

 which have made loop-shaped tubes joined by a median cavity. Together with 

 these are simple tubes of Palaeosabella. 



of tlieir entrance. Often the tubes adapt themselves to the 

 thickening or thinning valves, taking advantage of the for- 

 mer to recurve or loop, and compelled by the latter to flatten 

 down. The tendency to make a hook or loop, or to take on 

 the U-shape, is shown in many cases and the development 

 of a clavate form at the blind end is frequent and charac- 

 teristic. Most interesting beyond these features is the fact 



- n 



. 1 





Fig. 85. Cast of pouch-shaped (algal?) borings extending in from the surface of 

 a brachiopod shell, x 4. Oriskany sandstone (Lower Devonian). 



