326 



BITLLETIN- 7*7, UNITED STATES NATIONAL MUSEUM. 



memoration in a small way of Professor Hall's work upon fossil Bry- 

 ozoa, and particularly upon this generic group. 



The zoaria of Hallopora are almost always solid ramose and bushy. 

 In the perfect state the apertures are closed by perforated, orna- 

 mental covers which, as growth proceeds, form the diaphragms of 

 succeeding layers. 



Genotype. — CaUopora elegantula Hall. Early Silurian of America 

 and Europe. 



HALLOPORA MULTITABTJLATA (Ulrich). 

 Text fig. 202. 



Monotrypella muUitabulata Ulrich, Fourteenth Ann. Rep. Geol. Nat. Hist. Surv. 

 Minnesota, 1886, p. 100. 



CaUopora muUitabulata Ulrich, Geol. and Nat. Hist. Surv. Minnesota, vol. 3, 

 pt. 1, 1893, p. 280, pi. 23, figs. 11, 12, 16, 17, 24-26, 30, 31; Zittel's Textbook of 

 Paleontology (Eng. ed.), 1896, p. 274, fig. 456 C, D.— Sardeson, Journ. Geol., 

 vol. 9, 1901, p. 9, pi. A, figs. 5-6(7.— RxjEDEMANN, Bull. 49, New York State 

 Mus., 1901 [1902], p. 13.— NiCKLES, Kentucky Geol. Surv., Bull. 5, 1905, p. 

 42, pi. 1, fig. 2.— Bassler, Proc. U. S. Nat. Mus,, vol. 30, 1906, p. 22, pi. 1, 

 figs. 5-7. 



Several specimens in the collections from the Wassalem beds at 

 Uxnorm are externally and internally so similar to examples of Hal- 

 lopora multitalulata from the Black River and lowest Trenton rocks 

 of Minnesota that were the two lots mixed they could not be sepa- 



FiG. 202.— Hallopora multitabtjlata. a, view of typical specimen-, natural size; 6, surface of the 



SAME, X9; C, SURFACE OF A FINELY PRESERVED EXAMPLE, X18, SHOWmG THE ORNAMENTED, ZO(ECIAL 

 covers; d, VERTICAL SECTION, X9, EXHIBITING THE CHARACTERISTIC CRO\VDED TABULATION. BLACK 



River (Decorah) shales, St. Paitl, Minnesota. (After Ulrich.) 



rated. One of the Russian specimens is almost an exact duplicate 

 of the American specimen shown in figure 202 a, while the internal 

 structure shown in the vertical section, figure 202 d, is repeated in 

 the thui sections of the foreign form. 



The zoarium of Hallopora muUitabulata is of more or less irregu- 

 larly divided subcylindrical branches with rather strongly elevated 

 monticules. The zooecia at the surface are angular, thin-walled, 

 and in close contact, about eight in 2 mm. The apertures of the 



