MOLLUSCOIDA. 



[hki.. 



Fjg 483 — Heder 

 ella canaden- 

 sis. Magnified 



nitida, Ulrich, 1882, Jour. Cin. Soc. Nat. 



Hist., vol. 5, p. 166, Hud. Riv. Gr. 

 perelegans, Ulrich, 1878, (Ptilodictya 

 perelagans,) Jour. Cin. Soc. Nat. Hist., 

 vol. 1, p. 94, Hud. Riv. Gr. 



Hedkreli-a, Hall, 1884, Rep. 

 St. Geol., p. 53. [Ety. 

 htdera, ivy.] Bryozoum 

 parasitic, procumbent, 

 attached the entire 

 length ; main axis tubu- 

 lar, from which proceed 

 lateral tubular cells, 

 giving it the general ap- 

 pearance of Stomato- 

 pora. Type H. cana- 

 densis, 

 canadensis, Nicholson, 

 1873, (Alecto (?) cana- 

 densis,) Can. Nat. and Geol., vol. - 

 7, p. 144, and Pal. Prov. Ont., p. \ a / 

 124, Up. Held, and Ham. Gr. \W i 

 cirrhosa, Hall, 1884, Rep. St. 



to. 53, Ham. Gr. 

 conferta, Hall, 1884, (Ptilionella 

 conferta,) Rep. St. Geol., p. 56, 

 Ham. Gr. 

 filiformis, Billings, 1858, (Aulopora 

 filiformis,) Can. Jour., vol. 4, p. 

 119, Ham. Gr. 

 magna, Hall, 1884, Rep. St. Geol., 

 p. 55, Ham. Gr. 

 Helicopora, Clay pole, 1883, Quar. 

 Jour. Geo. Soc, p. 30. [Ety. helix, 

 spiral; poros, pore.] Bryozoum 

 expanded, fenestrate, and spiral ; 

 formed of slend. r, bifurcating 

 rays, poriferous on one face, con- 

 nected by nonporiferous bars, 

 forming an open net-work ; cells 

 arranged in two rows along the 

 rays, one row on each side of a 

 median keel ; axis none, or con- 

 sisting only of the thickened 

 inner border of the bryozoum, 

 not straight, but forming a 

 spiral, rounded, nonporiferous, or 

 slightly poriferous, inner margin. 

 Type H. latispiralis. Regarded 

 by some as a synonym for Fen- 

 estella, and distinguished only I ' IG - 48S - 

 by the spiral form. 

 archimrdiformis, Claypole, syn. for Ar- 

 chimedes lax us. 

 latispiralis, Clav- 

 pole, 1883, Quar. 

 Jour. Geo. Sci., 

 p. 32, Niagara Gr. 

 ulrichi, Claypole, 

 1883, Quar. Jour. 

 Geo. Soc, p. 33, 

 Up. Held. Gr. 

 Heliotrypa, Ulrich, 

 1883, Jour. Cin. 

 Fig. 484.— Heliotrypa bi- Soc. Nat. Hist., 



folia. Tangential sec- vol. 6, p. 277. 



[Ety. helios, sun ; 

 trupa, opening.] Bifoliate, interstitial 

 cells developed from the prostrate por- 



tion of the zocecia ; intercommunication 

 by means of radially arranged tubuli. 

 Type H. bifolia. 



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

 Hist., vol. 6, p. 278, Kaskaskia Of. 

 Helopora, Hall, 1852, Pal. N. Y., vol. 2, p. 

 44. [Ety. htlos, nail; poros, pore.] 

 Zoarium jointed ; segments small, sim- 

 ple, cylindrical, often swollen at the 

 extremities ; cells oval or subangular, 

 and arranged between longitudinal 

 elevated lines or in quincunx. Type 

 H. fragilis. 



armata, Billings, 1866, Catal. Sil. Foss. 

 Antic, p. 38, Anticosti Gr. 



bellula, Billings, 1866, Catal. Sil. Foss. 

 Antic, p. 38, Anticosti Gr. 



circe, Billings, 1866, Catal. Sil. Foss. 

 Antic, p. 39, Anticosti <ir. 



tion x 50. 



i-i, Helopora fragilis; f-h, Helopora lindstroml, 

 sections xA 



concava, Billings, 1866, Catal. Sil. Foss. 



Antic, p. 37, Anticosti Gr. 

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



Sur. Minn., p. 59, Trenton Gr. 

 formosa, Billings, 18(>r>, Catal. Sil. Foss. 



Antic, p. 37, Anticosti Gr. 

 fragilis, Hall, 1852, Pal. 



N. Y., vol. 2, p. 44, Clin- 

 ton Gr. 

 fragilis var. acadiensis, 



Hall, 1860, Can. Nat. FlQ . 4i 



and Geo., vol. 5, Anti- pora fragilis. 



COSti Gr Natural size 



irregularis', Billings, 1866, •»*»■«»«•«■ 



Catal. Sil. Foss. Antic, p. 39, Anticosti Gr. 

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



111., vol. 8, pi. 29, Hud. Riv. Gr. 



:l 



