NICKLES AND BASSLEK.] DIAGNOSES OF GP^NERA. 41 



Family ACANTHOCLADIID^ Zittel. 



Zoarium a pinnate or fenestrate expansion, celluliferous on one face 

 only, consisting of strong central stems which give off numerous 

 smaller, lateral branches from their margins; the lateral branches are 

 free or unite with those of the next stem; nonporiferous dissepiments 

 rarely present; zooecial characters mostly as in the Fenestellidre. 



PiNNATOPORA Vine (Glauconome of authors). 



Zoarium a small delicate stipe, with short, free lateral branches given 

 oli' frequently and at regular intervals; apertures in two rows, sepa- 

 rated by a moderate median keel. 



Genotype: Glauconome elegans Young and Young. Range, Devon- 

 ian-Carboniferous. Nineteen species. 



ACANTHOCLADIA King. 



Zoarium as in Pinnatopora, but larger and stronger and with three 

 or more rows of apertures between which the surface is elevated into 

 small longitudinal ridges or series of tubercules. 



Genotype: Ccratopkytes anceps Schlotheim. Carboniferous. One 

 species. 



Septopora Prout. 



Zoarium a fenestrate, flabellate or leaf -like expansion; primarj' 

 branches numerous, increasing by bifurcation or interpolation; the 

 lateral branches unite with those from the adjacent primary branches; 

 apertures in two rows on primary and lateral branches; reverse usually 

 with fine stride and scattered dimorphic pores. 



Genotype: Septopora cestriensis Prout. Mississippian, Carbonif- 

 erous. Eleven species. 



Synocladia King. 



Zoarium as in Septopora, but branches stronger and with three or 

 more rows of apertures, usually between elevated ridges. 



Genotype: Retepora virgulacea Phillip^s. No American species 

 known. 



Ptilopora McCoy (Dendricopora De Koninck). 



Zoarium pinnate, the stipe much stronger than the oblique lateral 

 ])ranches, which are occasionally and irregularly united by dissepi- 

 ments; apertures in two rows. 



Genotype: Ptilopora pliima McCoy. Devonian, Mississippian. 

 Eight species. 



ICHTHYORACHIS McCoy. 



Zoarium as in Ptilopora, but the stipe bears five or more rows of 

 apertures and the branches usually three. 



Genotype: Ichthyorachis nefweiihami McCoy. Silurian. One 

 species. 



