NicKLKs ANn liASM.En.] DIAGNOSES OF GENERA. 19 



Mesopokks (interstitial colls). — Tububir structures found between 

 the zocBcia; they are coramonl>^ angular or irregular in outline in 

 cross section. 



AcANTHOPORES (spiniforni corallites, spiniform tubuli). — Small 

 cylindrical tubes usually situated at the angles of junction of adjoin- 

 ing zocBcia, forming s'pine-like projections upon the surface. 



Vesicular Tissue. ^ — In a number of forms the space between the 

 zooecia is occupied by tissue composed of irregularly superimposed 

 vesicles. This probably served to give strength to the zoarium and 

 to protect the zooecia. 



DIAGNOSES OF SUBORDERS. FAMILIES, AND GENERA. 



Class BRYOZOA Ehrenberg. 



Order GYMNOL^^MATA Allman. 



Suborder OTENOSTOMATA Busk. 



Zooecia usually isolated and developed by Inidding from the inter- 

 nodes of a distinct tubular stolon or stem. Orifice terminal, with an 

 operculum of seta3. Zoarium horny or membranaceous. Marsupia 

 wanting. 



Family EHOPALONARIID^. 

 Rhopalonaria Ulrich. 



Fusiform segments (? stolons constricted fusiformly) arranged in a 

 more or less pinnate manner, impressed or almost embedded in the 

 host. Zooecia unknown. 



Genotype and only described species: Rhopalonaria venosa Ulrich. 

 Range, Ordovician-Devonian. A species ver}^ similar to the geno- 

 type occurs in the Clinton, and another undescribed species is found 

 in the Hamilton. 



Family ASCODICTYONID^ Ulrich. 

 AscoDiCTYON Nicholson and Etheridge, Jun. 



Zoarium parasitic, of thread-like ramifying stolons, with bulbous 

 enlargements, arranged irregularly or in stelliform clusters; surface 

 minutely punctate. Zooecia unknown. 



Genotype: Ascodictyon stellatum Nicholson and Etheridge, Jun. 

 Devonian. Two described species; also several undescribed species 

 from the Chester group. 



Vinella Ulrich. 



Zoarium parasitic, consisting of exceedingly slender, ramifying, 

 thread-like, tubular stolons, arranged more or less distinctly in a radial 

 manner. Surface of stolons sometimes faintly lined longitudinally 

 and with a row of widely separated small pores along the top. Zooecia 

 unknown. 



