ulrich-bassler] revision of paleozoic bryozoa 267 



A. stellatum Nich. & Ethr., Jr. Devonian— Hamilton formation. 



A. Horcale new species. Devonian — Hamilton formation. 



A. parvulnm new species. Mississippian — Chester group. 



A. sparsnm new species. ]\Iississippian — Chester group. 



A. youngi Vine. Carboniferous of Scotland. 



Position Doubtful. 

 Genus Ptychocladia new genus. 

 P. agelhis new species. Pennsylvanian. 



Family RHOPALONARHD^ Nickles and Bassler. 

 Genus Rhopalonaria Ulrich. 

 1879. Ropalonaria Ulrich, Jour. Cin. Soc. Nat. Hist., n, p. 26. 

 1882. Ropalonaria Ulrich, Ibid, v, p. i49- 

 1884. Rhopalonaria Vine (partim), Ann. Mag. Nat. Hist., sen 5, xiv, p. 



84, fig. iv. 

 1887. Rhopalonaria Vine (partim), Proc. Yorkshire Geol. and Polyt. Soc, 



IX, p. 185. 



1889. Rhopalonaria Miller, North Amer. Geol. and Pal., p. 321. 



1890. Rhopalonaria Ulrich, Geol. Surv. Illinois, viii, p. 367. 



1892. Rhopalonaria Vine, Proc. Yorkshire Geol. and Polyt. Soc, xii, p. 91. 

 1897. Rhopalonaria Simpson, Fourteenth Ann. Rep. State Geol. New 



York for 1894, p. 603. 

 1900. Rhopalonaria Nickles and Bassler, Bull. U. S. Geol. Surv., No. 

 173, P- 19- 

 Zoarium adnate, excavating the surface of the host so as to become 

 usually about half embedded in it; consisting, so far as known, of 

 fusiform internodes or cells connected by extremely delicate tubular 

 stolons, the whole arranged in a primate manner. Zocecia unknown, 

 probably deciduous and developed by budding from a subcentrally 

 situated pore in the internodes. 

 Genotype R. vcnosa Ulrich. 



The principal generic and family character is the faculty of ex- 

 cavating the body grown upon by the creeping base, the zoarium. 

 As a rule nothing remains except these clay filled or empty excava- 

 tions, but as they are sharp and true impressions of the stolons, and 

 the species are distinguished chiefly by variations in their dimensions, 

 the impressions serve quite as well in discriminating the species as the 

 more complete specimens. 



In the latter the stolons are in semi-relief and black in color, with 

 the pores and possibly other surface features generally more or less 

 obscured, or quite obliterated, by pyritization. 



The known species are all Paleozoic, the oldest occurring in the 



