PROBLEM OF THE MONTICULIPOROIDEA ' I 57 



the corresponding zooids or other structure was reduced to vir 

 tually an interautozooidal cortex. Comparison with Pacliydictya, 

 however, shows the ridges, and corresponding internal structures 

 to be mesopore walls in origin. The so-called tubuli seen in thin 

 section, corresponding to surface papillae, are then modifications 

 of mesopore walls. The autocell walls proper have none. The 

 so-called mesial tubuli are present. The autocell may have one 

 or two tabulae in the peripheral region, and at the upper angle, 

 between the axial and peripheral cell, a small hemiseptum may 

 appear. 



Similar species to the above described as to frond, compose 

 the genus Stictoporella, one of which is peculiar and further 

 instructive : 



Stictoporella cribrosa Ulr. 1 is bifoliate with branches about 2 mm 

 in width, which bifurcate and anastimose rapidly, growing thus 

 to a laro^e broad frond with numerous oval so-called fenestrules 

 (Plate B, Figs. 7, 8, and 9). The zoarial growth from cell increase 

 is at the branch ends, the margins of the branches, i. e., around 

 the fenestrules very quickly becoming static as to cell increase, 

 although with age the thickening from cell lengthening extends 

 them, constricting or even closing the fenestrules. 



Normally the downward end of the initial branch is pointed 

 with striated solid beveled surface, which is supposed to have 

 articulated into the crater-like socket of a striated non-cellulif- 

 erous basal expansion, forming a movable joint. The wide- 

 spreading zoarial branches coalesce with other zoaria of the same 

 and different species so freely that this joint must have been 

 usually immovable. When part of the zoarium died out, it was 

 regrown by a laminar cell growth, or again fragments of a 

 zoarium grew a new one, in which case a basal expansion unlike 

 the first was developed, or again the fragment became the basal 

 to a lateral fenestrated sporadic growth. 



Cell increase is at the growing margin from a mesial plane, 

 as in Pacliydictya, but the prostrate thin-walled part of the cell 

 is long, overlapping, so that in transverse section the axial 



I This appears to be the Clalhropora flabellata Hall ! 



