206 CALCAREOUS SPONGES. 



to 10 mm. in length and from 2 to 3"5 mm. in thickness. The canals opening on the 

 outer surface are from '18 to -2 mm. in width ; they can only be traced for a distance 

 of about -5 mm., where they appear to terminate in the interior spicular tissues. The 

 spicular rays are conical, acutely pointed, and occasionally with minutely spinous 

 surfaces. The longest measured is T4 mm. In cross section the rays are circular, 

 with a maximum thickness of -035 mm. The specimens throughout are calcareous. 

 Distribution. Upper Jura: probably from Thurnau, Bavaria. 



