Number 3 - Geological Curators Group

.fractures, and cracks can be made good with acement made of cellulose lacquer, 'Lithophon'(no longer used; a powdered meal of organicand~~ ~ ~inorganic comoonents) and oowderedm~ -~ ~colouring matter, and if necessary syntheticresin.A practical exampleIchthyosaur fragments in a slab from theUnteren Stein of Holzmaden were prepared withacid (Fig.7). This specimen was made easierto deal with by levelling the surface, and bycarefully watching the progress of treatmentand the behaviour of the bones duringtreatment and consolidation. Treatmentrequired 91.5 hours in acid and 250 hours inwater (frequently changed) to remove theacid. The result. was an average dissolutionof 7-8mm of matrix, corresponding to acontinuous rate of 0.07mm per hour (the rate,however, falls away' sharply when the acidgrows weaker and is not really measurable).Verv thin lavers of shale or of harder rockenciosed in the limestone delayed theprocess, but frequent renewal of the acidconsiderably encouraged the treatment. Itwas necessary to interrupt preparation seventimes for a cycle of washing, drying, andconsolidation to remove the undissolved rock.Further examplesAn ichthyosaur mandible from the Arietenkalk(Lower Lias, Gryphaea limestone, Wiirttemherg)was extracted by acid. The limestone wasefficiently removed by the strongestconcentration (17%) of acetic acid. Therewas little insoluble residue, which requiredless frequent removal than in the previousexample from the Upper Lias. However, thin-irregular layers in the rock form toughcrusts which had to be regularly removed toensure uniform solution.ACKNOWLEDGEMENTTra~slated hy Mr A.C. Benton from theoriginal German article, Larcher, F. andKeller, T., 1976. Praparationstechniken desLias-epsilon-Schiefers. Praparator, 22,213-220. Some of the tradenames of resins,etc., mentioned in the original German havebeen omitted as they are unavailable in thiscountry. I am grateful to Fritz Lorcher,Thomas Keller, and the publishers ofPraparator for permission to use theirarticle and photographs, to Thomas Keller forchecking the translation, and to the AreaMuseum Council for the South West for payingtranslation charges. - M.A. Taylor.Herr R. Uttenweiler (Dotternhausen) providedFigs.2, 3A, 4-6.McGowan, C. 1973. The cranial morphology ofthe Lower Liassic latipinnateichthyosaurs of England. Bull. Brit.- Mus. nat. Hist. (-.l, 24, 1-109. [A'Carbowax' method for reconstructionwork on original bony elements etchedout by acid is described on p.106 etseq.1.Rixon, A.E. 1968. The development of theremains of a small Scelidosaurus from aLias nodule. Museums Jl, 67, 315-320.Toombs, H.A. and Rixon, A.E. 1959. The useof acids in the preparation ofvertebrate fossils. Curator, 11,304-312.Fritz LorcherandThomas KellerPalaanthrop. Abt.Forschungsinstitut SenckenbergSenckenberganlage 256000 Frankfurt 1West GermanyTranslation received from M.A. Taylor 29 August 1984.