CKLEs AND BAssLER.] DIAGNOSES OF GENERA. 49 



PnyLLODicTYA lUrich. 



Zoariiini simple or irro^ularl}^ In'anchcd, growing from an expanded 

 basal attaehment; zooecia long, tubular, with diaphragms Imt no hemi- 

 septa, bending very gradually outward from the central axis, thus 

 causing the apertures to be more or less strongl}' oblique, with the 

 posterior edge liplike; interspaces wide, subsolid, traversed vertically 

 by one or two rows of minute tubuli, which appear as papilla3 at the 

 surface. 



Genotype: PhyUodictya frondosa Ulrich. Ordovician. Two spe- 

 cies. 



EuspiLOPORA Ulrich. 



Zoarium consisting of small, irregularly divided branches, with ser- 

 rated ov wavy edges; apertures in four or more linear series on the 

 middle of the branch, between slightly elevated longitudinal ridges 

 bearing numerous small nodes; alternately on the two sides are short 

 rows directed obliquely upAvard; between the ends of the zooecia shal- 

 low, lenticular vesicles are found; interspaces traversed verticalh" by 

 numerous minute tubuli. 



Genotype: Eimpilopiyra serrata Ulrich, Devonian. Four species. 



DiCRANOPORA Ulrich. 



Zoarium jointed; segments ligulate, rarely simple, usuall}' bifurcat- 

 ing at the upper end; each extremity somewhat thickened; minute 

 structure of zooecia and arrangement of apertures as in Rhinidictya. 



Genot3^pe: Ptllodlctya interiwdia Miller and Dj^er. Ordovician, 

 Silurian. Five species. 



GoNiOTRYPA Ulrich. 



Zoarium with a prominent median ridge upon both sides of the 

 double-leaved segments; otherwise like Dicranopora, 



Genotype and only known species; GonlvtryjKi hilateralis Ulrich. 

 Ordovician. 



Trigonodictya Ulrich. 



Zoarium of triangular })ranches, constructed upon the plan of Pris- 

 mopora, but with zooecia and all minute details of structure as in 

 Pachydictya. 



Genot3'pe; T/'i(/o)iod/'ctyaco?iciliatrix Ulrich. Ordovician, Silurian. 

 Two described and two new species. 



Family CYSTODICTYONID.aE Ulrich. 



Zoarium consisting of two or three layers of cells grown together 

 back to back, forming branching, fenestruled, or entire leaf-like 

 Bull. 173 4 



