34 PROCEEDINGS OF THE NATIONAL MUSEUM vol.87 



and arrangement of the zooecial tubes. The type specimen, which 

 incrusts a Cystiphyllum over a space of at least 10 sq. cm., shows the 

 same unusually regular arrangment throughout the single zoarium 

 of which it is composed. Zooecial tubes short, slightly curved, emerg- 

 ing at an angle of about 45°, very delicately lined transversely, and 

 with terminal transverse oval aperture slightly raised. Zoarial 

 branching at intervals of 3 to 5 mm. Zooecial diameter 0.15 mm., 

 length 0.6 mm.; 6 tubes in 5 mm. Compared with other species, 

 H. regularis is not so delicate as H. delicatula and is smaller than 

 H. parvirugosa. 



Occurrence. — Hamilton group: Thedford, Ontario (holotype) (Wid- 

 der shale); 3 miles west of East Bethany, N. Y. (Centerfield shale). 



Holotype— V.S.N M, Nos. 26575, 94558. 



HEDERELLA ARACHNOIDEA Clarke. 1900 



Plate 13, Figure 7 



Hederella arachnoidea Clarke, Mem. New York State Mus., vol. 3, No. 3, p. 61, 

 pi. 9, fig. 11, 1900. 



Only the type specimen, a zoarium incrusting the inner surface of a 

 trilobite glabella, has been found, but it shows relationship to the 

 H. canadensis group, differing from other small species in the consid- 

 erable length of its branches and the regularity with which the zooecia 

 arise alternately from the branch. Length of zooecia 1.3 mm., 

 width of zooecia 0.25 mm.; branching at intervals of about 5 mm., 

 often at nearly right angles, with zooecia arising at angle of about 

 35°; 4 zooecia in 5 mm. 



H. concinna is a related species but has smaller dimensions. H. 

 parvirugosa is perhaps still closer but its zooecia are shorter, more 

 rapidly expanding, and wider at their extremity. 



Occurrence. — Oriskany sandstone: Becraft Mountain, near Hud- 

 son, N. Y. 



Plastoholotype.—V.S.'N.M. No. 93957. 



HEDERELLA CIRRHOSA Hall. 1881 



Plate 6, Figures 1-8 



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

 p. 194, 1881); Rep. vState Geol. New York for 1883, p. 53, 1884.— Hall 

 and Simpson, Pal. New York, vol. 6, p. 277, pi. 65, figs. 12, 13, 1887.— 

 Simpson, 14th Ann. Rep. State Geol. New York, 1894, pi. 25, figs. 10, 11, 

 1897.— Whiteaves, Contr. Can. Pal., vol. 1, pt. 5, p. 381, 1898. — Bassler, 

 in Cleland, Wisconsin Geol. Nat. Hist. Surv., Bull. 21, sci. ser. 6, p. 57, pi. 6, 

 figs. 4, 5, 1911.— Stewart, Geol. Surv. Ohio, ser. 4, BuU. 32, p. 26, pi. 1, 

 fig. 18, 1927. 



Hederella canadensis Hall and Simpson (part). Pal. New York, vol. 6, pi. 65, 

 fig. 4, 1887. 



I 



