THE HEDERELLOIDEA — BASSLER 31 



HEDERELLA CANADENSIS GROUP 



Zoarium consisting of a single, narrow, tubular axis formed of the 

 initial portions of successive zooecia branching at rather regular 

 angles and distances, with the zooecial tubes arising one at a time 

 alternately to right and left from about the middle of the side of the 

 preceding one. For comparative purposes the 34 species here de- 

 scribed under tliis group are arranged under four headings: (1) The 

 typical section with 13 species with small zooecia, (2) the ten species 

 grouped around H. vagans, with wider unilinear branches loosely 

 subdividing and budding at long intervals, (3) three species with 

 long straight tubes as in H. blainvillei, and (4) nine species character- 

 ized by H. thedfordensis, with a robust zoarium of rather long, wide, 

 frequently budding zooecia. 



Hederella canadensis section 



HEDERELLA CANADENSIS (Nicholson. 1874) 



Plate 7, Figures 2-4 



Alecto ? canadensis Nicholson, Can. Nat., ser. 2, vol. 7, p. 146, 1874. 



Aulopora ? canadensis Nicholson, Pal. Prov. Ontario, p. 124, fig. 57a-e, 1874. 



Hederella canadensis Hall, Trans. Albany Inst., vol. 10, p. 194, 1883 (abstract, 

 p. 194, 1881); Rep. State Geol. New York 1883 p. 53, 1884.— Miller, North 

 Amer. Geol. Pal., fig. 483 (p. 308), 1889.— Whiteaves, Contr. Can. Pal., 

 vol. 1, p. 210, pi. 28, figs. 8, 8a, 1891.— Simpson, 14th Ann. Rep. State Geol. 

 New York, 1894, pi. 25, figs. 12, 13, 1897.— Grabau, Bull. Buffalo Soc. 

 Nat. Sci., vol. 6, p. 178, fig. 77, 1899. Not Hederella canadensis Hall and 

 Simpson, Pal. New York, vol. 6, pi. 65, figs. 1-7, 14, 16, 1887 (includes various 

 species from the Hamilton at York, N. Y., as follows: Figures 1, 6, and 8 = H. 

 filiformis (Billings, 1859); 2 = H. thedfordensis n. sp.; 3 = H. parallela n. sp.; 

 4=/f. cirrhosa Hall, 1881; 5, 7 = H. delicatula n. sp.; 14=//. vagans n. ep.; 

 16 = //. contortilis) . 



Specimens from both the Onondaga limestone and the Hamilton 

 shales were included among the original figured types of this species, 

 but the original of figure 57c of Nicholson's illustration is here selected 

 as the holotype, as it appears to be the most accurate drawing and, 

 moreover, agrees exactly with a topotype in the U. S. National Mu- 

 seum collections identified by Nicholson himself. As thus restricted, 

 H. canadensis is a slender, delicate species occurring usually as molds 

 in the siliceous Onondaga fossils of Ontario, but gutta-percha squeezes 

 furnish excellent representations of the surface. The zoarium in- 

 crusts cup corals and other objects and consists of a narrow tubular 

 axis, which branches at rather regular intervals of about 5 mm. at an 

 angle of 30°, from which the zooecia are given off alternately to the right 

 and left at distances averaging 1.2 mm. ; measuring on the same side of 

 the axis 3 to 4 zooecia occur in 5 mm. The zooecial tubes are indis- 

 tinctly annulated, are about 0.2 mm. in diameter and 0.7 mm. long, 

 with the aperture terminal, transversely oval; they arise from the 



