898 PALAEONTOLOGY OF ILLINOIS. 



with fine striae, and a variable number of scattered dimorphic 

 pores. Celluliferous side, with two rows of zocecia arranged as 

 in Pinnatopora. Apertures large. 



Type: S, cestriensis Prout. Range, Chester, Lower and Upper 

 Coal Measures. 



ACANTHOCLADIA King. Zoaria like those of Pinnatopora, but 

 larger and with three or more rows of cells. Between these the 

 surface is elevated into small longitudinal ridges or series of 

 tubercles. 



Type: A. anceps Schlotheim. Range, Upper Coal Measures to 

 Permian. 



SYNOCLADIA King. This genus differs from Acanthocladia in 

 the same manner as Septopora does from Pinnatopora, in 

 having the lateral branches of adjacent stems unite with each 

 other, thereby forming of the whole a fenestrated frond. 



Type: S. virgulacea King. Permian. 



DIPLOPORA Young & Young. Zoaria consisting of very slender- 

 straight stems, which throw off a few lateral branches of equal 

 dimensions; Cells in two rows. Median keel moderately de- 

 veloped. 



Type: D. marginalia Y. & Y. Range, Chester and Coal Meas- 

 ures. 



PTILOPORA McCoy. Zoaria pinnate, the median branch 

 stronger, particularly on the reverse, than the oblique lateral 

 branches. The latter are united to each other at frequent in- 

 tervals by non-poriferous dissepiments. Zocecia in two ranges. 



(?) Type: Retepora flustriformis Phillips (P. prouti Hall, is a 

 typical form.) Range, Hamilton to St. Louis. 



Icthyorachis McCoy, Penniretepora D'Orb., and Ramipora 

 Toula probably belong here. 



Family SPHRAGIOPORID.E n. fam. 

 Zoaria parasitic; zooecia of the same type as in the FENE- 



STELLID,E. 



SPHRAGIOPORA n. gen. Zoaria parasitic, forming very small, 

 sub-hemispheric patches on foreign bodies. Zooecia with circular 



