PTI.] 



MOLLUSCOIDA. 



319 



obliqua, Ringueberg, 1884, (Stictopora 

 obliqua,) Proc Acad. Nat. Sci., p. 146, 

 Clinton Gr. Not well denned. 



parallela, Hall, 1887, Pal. N. Y., vol. 6, p. 

 270, Ham. Gr. 



Pig. 504 —Ptilodictya pavonia. Natural size, 

 and magu i fled. 



pavonia, D'Orbigny, 1850, Prodr. de 



Paleont., t. 1, p. 22, Hud. Riv. Gr. 

 perelegans, see Graptodictya perelegans. 

 plumaria, James, 1882, (as figured by Ul- 

 rich,) Jour. Cin. Soc. Nat. Hist., vol. 5, 

 pi. 7, Hud. Riv. Gr. 

 plumea, Hall, 1887, Pal. N. Y., vol. 6, p. 



271, Ham. Gr. 

 punctata, Nicholson & Hinde, 1874, Can. 



Jour., p. 7, Clinton Gr. 

 ramosa, til rich, 1882, Jour. Cin. Soc. Nat. 



Hisl., vol. 5, p. 164, Trenton Gr. 

 retiformis, Hall, 1887, Pal. N. Y., vol. 6, 



p. 272, Ham. Gr. 

 rustica, see Stictopora rustica. 

 scutulata, Hall, 1884, (Stictopora scutu- 

 lata,) Rep. St. Geol., p. 47, Ham. Gr. 

 serrata, see Prismopora serrata. 

 subrecta, Ulrich, 1886, 14th Rep. Geo. 



Sur. Minn., p. 63, Trenton Gr. 

 sulcata, Billings, 1886, Catal. Sil. Foss. 



Antic, p. 35, Anticosti Gr. 

 superba, Billings, 1866, Catal. Sil. Foss. 



Antic, p. 35, Anticosti Gr. 

 symmetra, Safford. Not defined, 

 tarda, Billings, 1874, Pal. Foss., vol. 2, p. 

 13, Gaspe Limestone No. 8, Devonian. 

 tenera, see Stictopora 



tenera. 

 tenuis, see Phaeno- 



pora tenuis, 

 triangulata, White, 

 1878, Proc. Acad. 

 Nat. Sci., p. 35, and 

 Cont. to Pal. No. 6, 

 p. 131, Coal Meas. 

 variabilis, Ulrich, in- 

 stead of P. nodosa, 

 James, that was pre- 

 occupied, Hud. Riv. 

 Gr. 

 whiteavesi, Ulrich, (in 

 press,) Micropahe- 

 ontology, p. 18, 

 Hud. Riv. Gr. (?) 

 there is no series of p T i L OPORA,McCoy,1844, 

 median mbuh. g yn< ' Carh /' Fos8 [ 



Ireland, p. 200. [Ety. plilon, plume; 

 poros, pore.] Flabelliform attached by 

 roots, from which a strong midrib 



Fig. 505.— Ptilodictya 

 variabilis. Trans- 

 verse section x 50, 

 showing the basal 

 portion of the two 

 layers of zocecin, 

 and the duplex 

 character of the 

 median lamina. 

 Between the plates 



arises, giving origin on each side to 

 thin, equidistant rays, connected by 

 regular dissepiments ; external face of 

 the rays carinate and bearing two rows 

 of pores. Type P. flustriformis. 



acuta, Ulrich, (in press,) Geo. Sur. 111., 

 vol. 8, pi. 65, Burlington and Keo- 

 kuk Gr. 



cylindracea, Ulrich, (in press,) Geo. Sur. 

 UK, vol. 8, pi. 66, Keokuk Gr. 



infrequent, Hall, 1887, Pal. N. Y., vol. 6, 

 p. 281, Ham. Gr. 



nodosa, Hall, 1884, Rep. St. Geol., p. 59, 

 Ham. Gr. 



paupera, Ulrich, (in press,) Geo. Sur. 111., 

 vol. 8, pi. 66, Keokuk Gr. 



prouti, Hall, 1858, Geo. Rep. Iowa, p. 653, 

 Warsaw Gr. 



striata, Hall, 1884, Rep. St. Geol., p. 58, 

 Ham. Gr. 



valida, Ulrich, (in press,) Geo. Sur. 111., 

 vol. 8, pi. 65 and 66, Keokuk Gr. 



Fig. 506.— Ptilodictya variabilis. Vertical section 

 x35, showing hemisepta. 



Ptiloporella, Hall, 1887, Pal. N. Y., vol. 

 6, p. xxiv. [Ety. from the genus Ptilo- 

 pora.~\ Bryozoum growing in the 

 same manner as Ptiloporina, but with 

 only two ranges of cell apertures on 

 the branches. Type P. laticrescens. 

 inajqualis, Hall, 1887, Pal. N. Y., vol. 6, p. 



171, Up. Held. Gr. 



laticrescens, Hall, 1887, Pal. N. Y., vol. 6, 

 p. 171, Up. Held. Gr. 



nervata, Nicholson, 1875, (Fenestella 

 nervata,) Ohio Pal., vol. 2, p. 264, Nia- 

 gara Gr. 

 Ptiloporina, Hall, 1887, Pal. N. Y., vol. 6, 

 p. xxiv. [Ety. from the genus Ptilo- 

 pora.~] Resembling Fenestella, some 

 branches larger than others; ordinary 

 branches originate laterally from one 

 or both sides of the primary branches, 

 not bifurcating as in ordinary forms of 

 Fenestella ; cell apertures in three or 

 more ranges. Type P. conica. 



conica, Hall, 1887, Pal. N. Y., vol. 6, p. 



172, Up. Held. Gr. 



disparilis, Hall, 1887, Pal. N. Y., vol. 6, 



p. 173, Up. Held. Gr. 

 pinnata, Hall, 1887, Pal. N. Y., vol. 6, p. 



172, Up. Held. Gr. 



