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ThematerialdealtwithinthispaperwascollectedfromfourmeasuredsectionsatHuangutan ,ZiyangofShaanxi,atJiannigouandAnzigou ,TewoofsouthwesternGansuandatXiaohulishan ,EjinQiofnorthwesternInnerMongolia (Textfig .1) .AtHuangutan ,theSilurianrocksconsistofcarbonaceousmudyandsiltyslates ,about 4 7mthick .ThebaseandthetopofthesectionarebothfaultedagainsttheLowerOrdovicianbeds.GraptolitesobtainedincludePristiograptus pseudodubius (Boucˇek ) ,P .shaanxiensissp .nov .,P .vulgaris (Wood) ,P .cf.tumescens (Wood)andSaetograptussp .indicatingalateWenlock earlyLudlowage .AtAnzigou ,graptolitesarepreservedinsiltyandcalcareousslates,whichwereprevi ouslyassignedtotheLlandoveryAnzigouFormation .Af tercriticalidentification ,thegraptolitefaunaiscomposedofonlythreeearlyLudlowspecies :Saetograptussp .,Pristiograptusforbesi (Berry)andP .jaegeriHolland ,RickardsandWarren .AtJiannigou ,acollectionwasmadefromsandyslatesoftheLudlowHongshuigouFor mation,containinggraptolitesBohemograptusbohemicus(Barrande )andLobograptus progenitorcudalensisRickardsetal.AtXiaohulishan ,lateWenlock earlyLud lowbedsaremainlycomposedofgraywackesandsiltyslatesyieldinggraptolitesPristiograptusjaegeriHollandetal.,P .pseudodubius(Boucˇek) ,P .parvusUlstandMonograptusuncinatusTullberg .Specimensarepoorlypreserved ,butworthwhilereporting ,aslateWenlock ear lyLudlowgraptoliteshavelittlebeenknownfromthevastareaofNorthwestChina .Heretotallyelevenspecies ,be longingtofivegenera,ofHomerian (UpperWenlock)andGorstain (LowerLudlow) graptolitesaredescribedandre viewed ,ofwhichPristiograptuspseudodubius(Boucˇek) ,P .vulgaris (Wood) ,P .forbesi (Berry) ,P .jaegeriHollandetal.,P .parvusUlstandLobograptusprogen itorcudalensisRickardsetal.arerecordedinChinaforthefirsttime .ThedescriptionofanewspeciesofPris tiograptusisasfollows