. Bulletin - United States National Museum. Science. 284 BULLETIN 77, UNITED STATES NATIONAL MUSEUM. HEMIPHRAGMA IRRASUM (Ulrich). Text figs. 172, 173. Batostoma irrasa Ulrich, Fourteenth Ann. Rep. Geol. Nat. Hist. Surv. Minnesota, 1886, p. 94. nemiphragma irrasum Ulrich, Geol. and Nat. Hist. Surv. Minnesota, vol. 3, pt. 1, 1893, p. 299, pi. 24, figs. 5-19; Zittel's Textbook of Paleontology (Eng. ed.), 1896, p. 275, fig. 460.—Simpson, Fourteenth Ann. Rep. State Geologist ol New York for the Year 1894, 1897, p. 592, figs. 190-193. This very abundant American Black River species is represented i
. Bulletin - United States National Museum. Science. 284 BULLETIN 77, UNITED STATES NATIONAL MUSEUM. HEMIPHRAGMA IRRASUM (Ulrich). Text figs. 172, 173. Batostoma irrasa Ulrich, Fourteenth Ann. Rep. Geol. Nat. Hist. Surv. Minnesota, 1886, p. 94. nemiphragma irrasum Ulrich, Geol. and Nat. Hist. Surv. Minnesota, vol. 3, pt. 1, 1893, p. 299, pi. 24, figs. 5-19; Zittel's Textbook of Paleontology (Eng. ed.), 1896, p. 275, fig. 460.—Simpson, Fourteenth Ann. Rep. State Geologist ol New York for the Year 1894, 1897, p. 592, figs. 190-193. This very abundant American Black River species is represented in the Russian collection by a large zoarium which, as a comparison of figures 172 and 173 will show, has a structure practically identical. Fig. 172.—HEMIPHRAGMA IRKASXTM. /, VTEWS OF THE MINNESOTA TYPES, AFTER ULRICH. a AND 6, TWO FRAGMENTS, NATURAL SIZE, SHOWING DIFFERENCE IN SIZE AND BRANCHING; C, SURFACE OF AN AVER- AGE EXAMPLE, X9; d AND 6, TANGENTIAL SECTIONS, X18, EXHIBITING RANGE OF STRUCTURE NOTED IN VARIOUS PARTS OF THE ZOARIUM; /, VERTICAL SECTION OF BRANCH, X9. BLACK RiVEE (DECORAH) SHALES, Minneapolis, Minnesota. with that of Ulrich's types. In fact, this specimen differs only in the greater size of its branches, a difference due entirely to age. Ulrich has given the following description of HemipTiragma irrasum: Zoarium consisting of small, subcylindrical, frequently and rather irregularly divid- ing branches, commonly 5 or 6 mm. in diameter, but varying from 4 to 8 mm., the latter extreme probably only when an extra layer of tubes has grown over the original branch. Monticules wanting, but under fully matured conditions the surface is abun- dantly spinulose. Zooecia with subangular apertures, and thin walls when young,. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original United States National
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