928 BULLETIN 92, UNITED STATES NATIONAL MUSEUM. 



PACHYDICTYA Ulrich. Genotype: P. robusta Ulrich. 



Pachydictya Ulrich, Jour. Cincinnati Soc. Nat. Hist., 5, 1882, p. 152.— Foerste, 

 Bull. Sci. Lab. Denison Univ., 2, 1887, p. 162 —Miller, N. A. Geol. Pal., 1889, 

 p. 313— Ulrich, Geol. Surv. Illinois, 8, 1890, pp. 390, 522; Geol. Minnesota, 3, 

 1893, p. 145.— Pocta, Syst. Sil. Centre Boheme, 8, pt. 1, 1894, p. 15.— Simp- 

 son, 14th Ann. Rep. State Geol. New York for 1894, 1897, p. 530.— Nicklesand 

 Bassler, Bull. U. S. Geol. Surv., 173, 1900, p. 48— Hennig, Archiv. fur Zool., 

 K. Sven. Vet.-Akad. Stockholm, 2, No. 10, 1905, p. 25— Bassler, Bull. U. S. 

 Geol. Surv., 292, 1906, p. 57.— Grabau and Shimer, N. A. Index Fossils, 1, 

 1907, p. 159.— Cumings, 32d Ann. Rep. Dep. Geol. Nat. Res. Indiana, 1908, 

 p. 751.— Bassler, Bull. U. S. Nat. Mus., 77, 1911, pp. 137, 138. 



Pachydictya acuta (Hall). 



Stictopora? acuta Hall, Pal. New York, 1, 1847, p. 74, pi. 26, figs. 3a-b .—Billings, 

 Canadian Nat. Geol., 1, 1856, p. 317. — Lesley, Geol. Surv. Pennsylvania, 

 Rep. P 4, 1890, p. 1063, figs.— Ulrich, Jour. Cincinnati Soc. Nat. Hist., 5, 1882, 

 p. 168, pi. 8, figs. 1-lb. 



Ptilodictya acuta Nicholson, Pal. Province Ontario, 1875, p. 12, fig. 3. — Billings, 

 Canadian Nat. Geol., 1, 1856, p. 318, fig. 5; Geol. Canada, Geol. Surv. Canada, 

 1863, p. 158, fig. 121.— Emmons, Amer. Geology, 1, pt. 2, 1855, pi. 7, figs. 3a-c; 



Pachydictya acuta Ulrich, 14th Ann. Rep. Geol. Minnesota, 1886, pp. 75, 76; 

 Contr. Micro-Pal. Cambro-Sil., pt. 2, 1889, p. 44, Geol. Minnesota, 3, 1893, 

 p. 155, pi. 8, figs. 11-17; pi. 9, fig. 7.— Grabau and Shimer, N. A. Index 

 Fossils, 1, 1907, p. 159.— Whiteaves, Pal. Foss., 3, 1897, p. 161. 



Trenton: Trenton Falls, etc., New York; Ontario; Kentucky; Iowa; Minnesota. 

 Manitoba; etc. 



Plesiotypes.—Cat. Nos. 43721, 44099, U.S.N.M. (Ulrich). 



Pachydictya Alcyone Billings. See Pachydictya crassa. 



Pachydictya arguta Ulrich. See Pachydictya crassa. 



Pachydictya bifurcata (Hall). 



Eschara bifurcata Van Cleve (MS.). 



Stictopora bifurcata Hall, 12th Aun. Rep. Indiana Geol. Nat. Hist., 1883, p. 267, 

 pi. 13, figs. 3, 4.— Lesley, Geol. Surv. Pennsylvania, Rep. P 4, 1890, p. L063, 



fig. 

 Pachydictya bifurcata Foerste, Bull. Sci. Lab. Denison Univ., 2, 1887, p. 163; 



ibid., 3, 1888, pi. 15, fig. 9; Geol. Surv. Ohio, 7, 1895, p. 599, pi. 28, fig. 9.— 



Bassler, Bull. U. S. Nat. Mus., 77, 1911, pp. 143-145, figs. 67, 68. 

 Stictopora scalpellum Eichwald (not Lonsdale), Lethssa Rossica, 1, 1860, p. 390, 



pi. 24, fig. 15a-c. 

 Rhinidictya? Borkholmiensis Wiman, Bull. Geol. Inst. Univ. Upsak, 5, pt. 2, 



1901, p. 180, pi. 6, figs. 1-7. 

 Silurian: Dayton, Fairhaven, etc., Ohio; Kentucky (Brassfield); various L ». - 1 1 L • 



ties in Esthonia, Russia (Lyckholm and Borkholm). 

 Plesiotypes— Cat. No. 57240, U.S.N.M. (Bassler). 



Pachydictya bifurcata iustabilis Foerste. 



Pachydictya bifurcata var. instabilis Foerste, Bull. Sci. Lab. Denison Univ., 2, 

 1887, p. 164; ibid., 3, 1888, pi. 15, fig. 10; Geol. Surv. Ohio, 7, 1S95, p. 599, 

 pi. 28, fig. 10. 

 Upper Medinan (Brassfield): Near New Carlisle, Ohio. 



Pachydictya conch a mix Ulrich. See Trigonodictya conciliatrix. 



