. Bulletin - United States National Museum. Science. FlG. 135.—BYTHOPORA SUBGEACILIS. O, AN ORDINAKY FRAGMENT, NATURAL SIZE; 6, SURFACE OF SPEa- MEN, X9; C, TANGENTIAL SECTION OF A POORLY PRESERVED FRAGMENT, X18; d, VERTICAL SECTION, X18. Rhinidictya bed OF Black River (Decorah) shales, St, Paul, Minnesota. (After Ulrich.) served examples from the type locahty have shown that cystiphragms are entirely wanting and that generically the species differs in no way from the other large forms of BytJiopora. The identification of this species in the Russian strata is based upon several well-pre- serve
. Bulletin - United States National Museum. Science. FlG. 135.—BYTHOPORA SUBGEACILIS. O, AN ORDINAKY FRAGMENT, NATURAL SIZE; 6, SURFACE OF SPEa- MEN, X9; C, TANGENTIAL SECTION OF A POORLY PRESERVED FRAGMENT, X18; d, VERTICAL SECTION, X18. Rhinidictya bed OF Black River (Decorah) shales, St, Paul, Minnesota. (After Ulrich.) served examples from the type locahty have shown that cystiphragms are entirely wanting and that generically the species differs in no way from the other large forms of BytJiopora. The identification of this species in the Russian strata is based upon several well-pre- served specimens, agreeing in all respects with the typical Minnesota examples. The zoarium of Bythopora subgracilis is of small, ramose, subcylindrical, smooth branches 2 to 4 mm. in diam- eter. The zooecial apertures are oblique or long drawn out in young examples and more direct in older forms, eight in 2 mm. In the early stages acanthopores are few, but as the apertures become direct numerous small acanthopores are developed. Mesopores are about as numerous as the zocecia, which they often resemble so closely that it is difficult to distinguish them. Diaphragms are entirely wanting, as shown in the vertical sections figured 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 Museum; Smithsonian Institution; United States. Dept. of the Interior. Washington : Smithsonian Institution Press, [etc. ]; for sale by the Supt. of Docs. , U. S. Govt Print. Off.
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