NicKLES ANO BASsi.KR.] DIAGNOSES OK GENERA. 23 



Family CERAMOPORID^ Ulrich. 



Zoiirium variable; niacuhe or clusters of niesopores or of zocpcia 

 larger than usual at regular intervals; zooecia tul)ular, at lirst pros- 

 trate, continue oblii^uel}" or directly to the surface, often with a few 

 diaphragms; apertures commonly oblique, provided with a lunarium; 

 mesoporcs generally present, always irregular and usually without 

 diai)hragms; walls minutely porous, formed of intimately connected 

 and irreffularlv laminated tissue. 



"to" 



Cekamopora Hall. 



Zoarium discoidal, free or attached by the center of the base; under 

 surface with one or more layers of small, irregular cells; zocBcia radi- 

 ating out on the upper surface from a depressed center; apertures 

 obli(iue, iml)ricating; mesopores short, irregular, decreasing in num- 

 ber from center to margin. 



Genotype: C&ramojjora iDihricata Hall. Silurian. 



Ceramoporella Ulrich. 



Zoarium of incrusting layers, which by superposition ma}- form 

 masses; zocBcia short, tubular with thin walls; apertures oval, oblique, 

 the lunarium forming a hood; mesopores abundant, often completel}^ 

 encircling the zocecia. 



Genotype: Ceramojwrella distincta Ulrich. Ordovician. Nine 

 described and twenty new species. 



Crepipora Ulrich. 



Zoarium incrusting, lamellate or massive, or, in one species, form- 

 ing hollow branches; zooecia long, tubular, thin- walled, with dia- 

 phragms; apertures angular or subpyriform, lunarium not overarch- 

 ing, its ends usuall}' projecting; mesopores generally restricted to the 

 macula?, which are elevated or depressed. 



Genotype: Crepipora simulant Ulrich. Ordovician. Eight de- 

 scribed and six new species. 



Chiloporella Ulrich. 



Zoarium forming parasitic sheets, from which rise flabellate fi'onds 

 or compressed branches; zocecial tubes long, thin-walled, irregular in 

 shape in immature region, near the surface walls much thickened, 

 diaphragms rarely developed; apertures ovate, lunarium conspicuously 

 elevated; mesopores numerous. 



Genotype and only described species: F/fttulijwra fjiabellata Ulrich = 

 Cet'anwp(/i'a nichohmii James. Ordovician. 



