308 



MOLLUSCOIDA. 



[HEI,. 



FIG 483. Heder- 

 ella canaden- 

 sis. Magnified. 



tion of the zooecia ; intercommunication 

 by means of radially arranged tubuli. 

 Type II. bifolia. 



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



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

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

 44. [Ety. helos, 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 Gr. 



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. 



HEDERELLA, Hall, 1884, Rep. 

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

 hedera, 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. \ */ 



124, Up. Held, and Ham. Gr. \\l/ * 

 cirrhosa, Hall, 1884, Rep. St. Geol., \ / 



p. 53, Ham. Gr. V> f/ 



conferta, Hall, 1884, (Ptilionella \ /j 



conferta,) Rep. St. Geol., p. 56, I x / 



Ham. Gr. A '/ 



filiformis, Billings, 1858, (Aulopora V / 



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



119, Ham. Gr. V /. 



magna, Hall, 1884, Rep. St. Geol., V\ / 



p. 55, Ham. Gr. A / 



HELICOPORA, Claypole, 1883, Quar. \/ 



Jour. (feo. Soc., p. 30. [Ety. helix, Vr 



spiral; poros, pore.] Bryozoum 



expanded, fenestrate, and spiral ; 



formed of slender, 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 



bv some as a synonym for Fen- 



estella, and distinguished only ^^- 485.-o-^ Helopora^agilis ^ Helopora lindstromi, 



by the spiral form 

 archimediformis, 



Claypole, syn. for Ar- 

 chimedes laxus. 

 latispiralis, Clay- 

 le, 1883, Quar. 

 our. Geo. Sci., 

 p. 32, Niagara Gr. 

 ulrichi, Claypole, 



r. Jo 



Geo. Soc., p. 3 

 . Gr. 



pol 

 Jo 



1883, Quar. Jour. 

 33, 



Up. Held! " 

 HELIOTRYPA, Ulrich, 

 1883, Jour. Cin. 



FIG. 484. Heliotrypa bi- Soc. Nat. Hist., 



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



tion x 50. 



[Ety. helios, sun ; 

 iliate. 



trupa, opening.] Bifoliate, interstitial 

 cells developed from the prostrate por- 



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, 1865, 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. FlG . 486 _ 

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

 costi Gr. Natu 



irregularis, Billings, 1866, 



it .u nil 



and magnified. 



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

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

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



