92 ORGANIC DEPENDENCE AND DISEASE 



To a flattened tube with raised edges, giving the sugges- 

 tion of a distinct loop with the branches connected by a 

 thin diaphragm, we have on a previous occasion applied the 

 name Caulostrepsis taeniola. So far as our present knowl- 

 edge goes this has been seen only in strophomenoid brachio- 

 pods from the Lower Devonian of the Rhineland. 



Fig. 77. PalaeosabeUa prisca in a valve of the brachiopod Leptostrophia. From 

 the Grande Greve limestone (Lower Devonian); enlarged. 



Finally, it is worthy of note that the host-shells receive 

 these boring worms in various ways. Sometimes the para- 

 site starts at one surface and bores straight across to and 

 through the other surface. Again a number of worms may 

 commence their attacks simultaneously at the growing edge 

 of the shell and while they bore parallel to, and within the 

 shell surfaces, the shell grows on outward beyond the circle 



