. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology. I X- -â â s. V. \ Text-Figure 6. View of the Upper Devonian and Lower Mississippian section on the north face of Crown Mountain (CM) in the Lewis and Clark Mountains of northwestern Montana. Cliffed part of the exposure (the mountain's "crown") is the lower Allan Mountain Limestone bearing Tanaoblastus allanensis, n. sp. One of the major problems of using acetic acid, its slow reaction with the limestone matrix, was partly overcome either by heating the acid on a hotplate to a tem- perature between 110° and
. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology. I X- -â â s. V. \ Text-Figure 6. View of the Upper Devonian and Lower Mississippian section on the north face of Crown Mountain (CM) in the Lewis and Clark Mountains of northwestern Montana. Cliffed part of the exposure (the mountain's "crown") is the lower Allan Mountain Limestone bearing Tanaoblastus allanensis, n. sp. One of the major problems of using acetic acid, its slow reaction with the limestone matrix, was partly overcome either by heating the acid on a hotplate to a tem- perature between 110° and 130° F or by starting with hot water at this temperature. This elevated temperature increased the rate of reaction of acetic acid to about two- thirds the rate of cold, dilute hydrochloric acid, but still yielded excellent preserva- tion. At some of the Lodgepole blastoid lo- calities, there is a marked contrast between the type of preservation developed during natural weathering and that achieved by extraction using heated acetic acid. The best example of this condition is found at the Standard Creek Section (ST) on the slopes of Cave Mountain in the Gravelly Range of southwestern Montana (see Text- Fig. 1), where nearly 500 specimens of Ta naoblastus have been collected. Natural weathering of these blastoids has produced a rather coarse, granular, pitted surface on the posed portions of nearly all these specimens that has destroyed much of the finer detail of the ambulacra, oral and anal regions, and calyx ornamentation. If these specimens are extracted from the sur- rounding limestone matrix by using heated acetic acid, in most specimens the un- weathered parts are somewhat better pre- served than the weathered parts. In about 20% of the specimens, there is an extreme contrast in preservation (see Plate 1, Fig. 1). In these specimens, the unweathered parts of the theca show excellent preser- vation and remarkably fine detail, espe- cially of the ambulacral areas and
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Keywords: ., bookauthorharvarduniversity, bookcentury1900, booksubjectzoology
