300 



Family, Rhinidictyonidae UJrich. 



(Jciiotypo: Rhinidictya iiicholsoni Ulrich. Stictopora (part) Hall, Pal. 

 X(>\v York, 1. 1847. p. 78. Ulrich. Geol. Surv. Illinois, 8, 1890, p. 388. 



Khiiiidictya Ulrich, Join-. Cincinnati Soc. Nat. Hist, 5, 1882, p. 152. Hall 

 and Simpson, Pal. New York, 6, 1887, p. 20. Miller, N. A. Geol. Pal., 1889, p. 

 320. Ulrich, Geol. Minnesota, 3, 1893, p. 124. Procta, Syst. Sil. Centre 

 Boheme, 8 pt. 1, 1894, p. 15. Ulrich, Zittel's Textb. Pal. (Engl, ed.), 1896, p. 

 279. Simpson, 14th Ann. Rept. State Geol. New York for 1894, 1897, p. 

 G05. Nickles and Bassler, Bull. U. S. Geol. Surv., 173, 1900, p. 48. Grabau 

 and Shimer. N. A. Index Fossils, 1, 1907, p. 158. Cumings, 32d Ann. Rept. 

 Dept. Geol. Nat. Res. Indiana, 1908, p. 755. Bassler. Bull. U. S. Nat. Mus., 

 77, 1911, pp. 131. 132 : Zittel-Eastman Textb. Pal., 1913, p. 345. 



Zoarium bifoliate, continuous or jointed, consisting of compressed 

 branches or leaf-like expansions; occasionally trifoliate; zooecia subgradu- 

 ate, arranged longitudinally : orifices and apertures elliptical or subcircular, 

 sometimes a little truncated posteriorly ; median tubuli between the median 

 laminae and between the longitudinal rows of zooecia ; mesopores wanting, 

 but vesicular tissue often developed ; inferior and superior hemiseptum 

 sometimes present. The family has been redefined to include the new genus 

 Hemidictya which has both inferior and superior hemiseptum. 



ficnus Rhinidictya Ulrich. Genotype : Rhinidictya nicholsoni Ulrich. 

 Stictopora (part) Hall, Pal. New York, 1, 1847, p. 73. Ulrich, Geol. Surv. 

 Illinois, 8. 1890, p. 388. 



Rhinidictya Ulrich, Jour. Cincinnati Soc. Nat. Hist., 5, 1882, p. 152. Hall 

 and Simpson, Pal. New York, 6, 1887, p. 20. Miller, N. A. Geol. Pal., 1889, 

 p. 320. Ulrich, Geol. Minnesota, 3, 1893, p. 124. Procta, Syst. Sil. Centre 

 Boheme, 8, pt. 1, 1894, p. 15. Ulrich. Zittel's Textb. Pal. (Engl, ed.), 1896, 

 p. 279. Simpson, 14th Ann. Rept. State Geol. New York for 1894, 1897, p. 

 605. Nickles and Bassler, Bull. U. S. Geol. Surv., 173, 1900, p. 48. Grabau 

 and Shimer, N. A. Index Fossils, 1, 1907, p. 158. Cumings, 32d Ann. Rept. 

 Dept. Geol. Nat. Res. Indiana, 1^08, p. 755. Bassler, Bull. U. S. Nat. Mus., 

 77, 1911. pp. 131. 132 ; Zittel-Eastman Textb. Pal., 1913, p. 345. 



"Zoaria composed of narrow, compressed, dichotomously divided branches, 

 with the margins sharp, straight and essentially parallel ; attached to for- 

 eign bodies by a continuous expanded base. Zooecial apertures subcircular 

 or elliptical, arranged alternately in longitudinal series between slightly 

 elevated, straight or flexuous ridges, carrying a crowded row of small, blunt 

 spines. Space immediately surrounding apertures sloping up to summits 

 of ridges." (Ulrich.) 



Rhinidictya tahulata n. sp. Plate XII, Figs. 5-6. Zoarium consists of 

 bifoliated branching form, the branches rising from the margins ; the type 

 specimen is 3 mm. wide, .8 to 1.7 mm. in thickness midway between the 

 margins. The surface is even with an occasional subsolid area, formed by 

 the thickening of the zooecial intersperspaces of mature specimens. The 

 margins are thin, celluliferous, approximately parallel, except near the 

 bifurcations. 



