110 



BULLETIN 77, tlNITED STATES NATIONAL MUSEUM. 



In thin sections the large granules of the surface are seen to be the 

 ends of continuous thick acanthopore-like tubes composed of a 

 granular, black material quite different in structure from the usual 

 wall substance. These tubes follow the walls in their course to the 

 surface, but they are not limited to any particular tube or direction. 

 In some sections they are seen to cross diagonally from one side of a 

 cell wall to the other before reaching the surface. Tangential sections 



Fig. 40.— Fistulipoka prim^va. a, the type-specimen, natural size; 6, surface of same, X8, exhib- 

 iting A portion of a macula and surrounding ZOCECIA; C, tangential section, X20, SHOWING OBSCURE 

 LUNAEIUM AND NUMEROUS LARGE GRANULES; d, VERTICAL SECTION, X8; e, PORTION OF SAME SECTION, 

 X20. GLAUCONITE LIMESTONE (B2), PAWLOVSK, GOVERNMENT OF St. PETERSBtJRG. 



show irregularly rounded zooecia with thin walls separated by vesic- 

 ular areas with equally thin walls. Here the lunarium is as indis- 

 tinctly developed as at the surface, while the granular tubes are just 

 as clearly shown. 



The fistuliporoid vesicles and the large, dark granular structure of 

 this species are so unusual in an Ordovician bryozoan that compari- 

 sons with other species are unnecessary. 



