314 



MOLLUSCOIDA. 



[pet- PH.*:. 



Fig. 495.- Pale 



schaiu. of t\i In. 



amplectans, Hall, 1884, Rep. St. Geol., p. 

 7, Ham. Gr. 



aspera, Hall, 1876, syn. for P. maculata. 



bifoliata, syn. for Ptilodictya nebulosa. 



bilateralis, Hall, 1883, Rep. St. Geo., pi. 

 16, fig. 22-25, Low. Held. Gr. 



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

 p. 67, Low. Held. Gr. 



foliata, syn. for Piilodictva nebulosa. 



incrassata, Hall, 1879, 28th Rep. N. Y. 

 St. Mus. Nat. Hist., p. 121, Niagara Gr. 



incrustans, Hall, 1874, 26th Rep. N. Y. St. 

 Mus. Nat. Hist., p. 107, Low. Held. Gr. 



intercella, Hall, 1884, Rep. St. Geol., p. 5, 

 Ham. Gr. 



maculata, Hall, 1876, 28th Rep. N. Y. St. 

 Mus. Nat. Hist., p. 121, Niagara Gr. 



offula, Hall, 1876, 28th 

 Rep. N. Y. St. Mus. Nat. 

 Hist., p. 120, Niagara Gr. 

 pertenuis, Hall, 1884, Rep. 

 St. Geol., p. 7. Ham. Gr. 

 radiata, Hall, 1883, Rep. 

 St. Geol., p. 16, fig. 13-14, 

 Low. Held. Gr. 



reticulata, Hall, 1884, Rep. St. Geol., p. 6, 

 Ham. Gr. 



sphaerion, Hall, 1876, 28th Rep. N. Y. St. 

 Mus. Nat. Hist., p. 121, Niagara Gr. 



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

 36, Low. Held. Gr. 



variacella, Hall, 1884, Rep. St. Geol., p. 6, 

 Ham. Gr. 

 Pktalotbyi-a, Ulrich, (in press,) Geo. Sur. 

 111., vol. 8, p. 377. [Ety. petalos, spread 

 out ; trupa x an opening.] Bifoliate, con- 

 sisting of irregular, compressed branches 

 or simple fronds, celluliferous on both 

 sides; zocecial tubes prismatic, arising 

 from a strongly flexuous mesial line ; 

 apertures subcircular or polygonal ; 

 mesopore-like interspaces, that do not 

 differ in their tabulation from the zo- 

 oecia, may occur ; very small acantho- 

 pores (?) occupy 

 manyoftheangles 

 of junction. Type 

 P. compressa. 



compressa, Ulrich, 

 (in press,) Geo. 

 Sur. III., vol. 8, pi. 

 46, Ham. Gr. 



delicata, Ulrich, (in 

 press,) Geo. Sur. 

 HI., vol. 8, pi. 46, 

 Ham. Gr. 

 Petigopoha, Ulrich, 

 1882, Journal Cin. 

 Soc. Nat. Hist., 

 vol. 5, p. 155. 

 [Ety. petigo, scab; 

 poros, pore.] Small 

 patches adhering to foreign objects, with 

 a narrow nonporiferous band or ger- 

 minating membrane along the outer 

 margin ; no interstitial cells ; spiniform 

 tubuli present. Type P. gregaria. 



asperula, Ulrich, 1883, Jour. Cin. Soc. Nat. 

 Hist., vol. 6, p. 157, Hud. Riv. Gr. 



grpgaria, Ulrich, 1883, Jour. Cin. Soc. Nat. 



Hist., vol. 6, p. 155, Hud. Riv. Gr. 

 petechialis, Nicholson, 1875, (Chetetes 



petechialis,) Ohio Pal., vol. 2. p. 213, 



Hud. Riv. Gr. 



Fig. 496.— Pelittopora petechialis on h Moniirn- 

 11 porn : also, specimen greatly enlarged. 



Phacki.opok \, Ulrich, (in press,) Geo. Sur. 

 III., vol.8, p. 368. LEty. phakdot, bundle; 

 poroa, pore.] Zoarium articulated ; seg- 

 ments short, obconical, consisting of 

 two or more equal, conical zocecia, with 

 slightly contracted circular apertures. 

 Type P. pertenuis. 



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

 111., vol. 8, pi. 29, Trenton Gr. 



pertenuis, Ulrich, (in press. Geo. Sur. 

 111., vol. 8, pi. 29, Galena Gr. 

 I'u i sopor a, Hall, 1852, Pal. N. Y., vol. 2, 

 p. 46. [Kty. phaino, to open or make a 

 window ; poros, pore.] Zoarium form- 

 ing thin, broad, or ensiform expansions, 

 celluliferous on both sides ; cellules 

 oval and arranged between elevated 

 lines ; macula; often developed ; distin- 

 guished from Ptilodictya and Stictopora 

 by the absence of a nonporiferous, stri- 

 ated edge. Type P. explanata. 



Fio. 497.— Phsenopora constellata. (Sections x 50. 



constellate, Hall, 1852, Pal. N. Y., vol. 2, 



p. 47, Clinton Gr. 

 ensiformis, Hall, 1852, Pal. N. Y., vol. 2, 



p. 48, Clinton Gr. 

 excellens, Billings, 1866, (Ptilodictya ex- 



cellens,) Cat. Sil. Foss. Antic, p. 34, 



Anticosti Gr. 



