54 AMERICAN FOSSIL BRYOZOA. [bull. 1^3. 



Rhinopora Hall. 



Zoarium forming large, undulating bifoliate expansions, cellulif erous 

 on both sides; surface usually smooth, rarelj^ with solid monticules, 

 and traversed by slender, rounding, bifurcating ridges, which appear 

 as shallow grooves when the surface is worn; apertures nearly circular, 

 occupying the summits of prominent papillae; mesopores present, but 

 closed at the surface; large median tubuli in the mesotheca. 



Genotype: Hhinojpora verrucosa Hall. Silurian. Three species. 



DiAMESOPORA Hall, 



Zoarium ramose, of hollow stems lined internally b}^ an epitheca; 

 zooecia simple, hexagonal, or rhomboidal, with an oval orifice in the 

 anterior half, which with growth forms a tubular vestibule; apertures 

 with peristomes equally elevated or highest posteriorly; intervestibu- 

 lar spaces compact or horizontally laminated. 



Genotype: Diamesopora dicJwtoTna^A^M. Silurian. Five species. 



LiCHENALIA Hall. 



Zoarium a subcircular unilaminar expansion; zocecia prostrate; 

 elongate-subrhomboidal, with direct subtubular vestibules; apertures 

 rounded, with peristome much elevated on the posterior side; inter- 

 spaces depressed, ? cellulose. 



Genotype and only known species: Lichenalia concentHca Hall. 

 Silurian. 



Stictotrypa Ulrich. 



Zoarium ramose, not pointed at the base; branches dichotomously 

 dividing, narrow, compressed; apertures circular or elliptical, with 

 distinct, evenly elevated peristome; interspaces flat or concave, com- 

 posed of horizontally laminated solid tissue. 



Genotype: Stictopora similis Hall. Silurian. Three species. 



Suborder OHILOSTOMATA Busk. 



Zooecia oval, turbinate, urceolate, quadrate, or hexagonal, arranged 

 usually side by side; orifice more or less anterior, of less diameter than 

 the zooecium, closed b}^ a movable cover; ova commonly matured in 

 external marsupia: appendicular organs frequently present. 



Family PALESCHARID^ Ulrich. 

 Paleschara Hall. 



Zoarium forming thin incrustations upon Orthocerata and other 

 organisms; zooecia very short, direct, with thin walls; apertures (if 

 such they can be called) long hexagonal or polygonal. 



Genotype: Palescha7'a incrustans Hall. Range, Ordovician-Devo- 

 nian. Thirteen species. 



