Dicharax (?) fargesianus (Heude, 1885)

FIGUrEs 8B, 10C–D, 17A–B.

Alycoeus fargesianus HEUdE, 1885: 96, pL. 24, fIGs 3, 3a.

Alycaeus (Chamalycaeus) fargesianus — Kobelt & Möllendorff, 1897: 148. Alycaeus (Chamalycaeus) fargesianus — Kobelt, 1902: 355.

Types examined. MCZ 167229 (4 syNTypEs Of Alycaeus fargesianus), CHINa, TCHEN-k'EOU. ONE Of THE syNTypEs was a spECImEN Of Metalycaeus rathouisianus. THErEfOrE, a LECTOTypE (MCZ 167229) was sELECTEd TO avOId fUrTHEr mIsUNdErsTaNdING rEGardING THE NamE Alycaeus fargesianus. THE OTHEr TwO spECImENs Of A. fargesianus arE paraLECTOTypEs (MCZ 384422). ACCOrdING TO JOHNsON (1973) paraTypEs arE aLsO prEsENT IN THE NMNH (INv. NUmbEr: 472341). THEsE wErE NOT ExamINEd by Us.

Diagnosis. A smaLL spECIEs wITH aTypICaL (LOw, bLUNT) rIbs ON R2, bLUNT swELLING ON R3 aNd rOUNdEd pErIsTOmE.

Description. SHELL (FIGUrE 8B) GrEyIsH IvOry; sHELL OUTLINE rOUNdEd Or sLIGHTLy OvaL frOm dOrsaL vIEw, spIrE ELEvaTEd, EdGE Of bOdy wHOrL Is rOUNdEd; prOTOCONCH (FIGUrEs 10C–D) LOw, IT was vIsIbLE IN ONE sHELL ONLy (OTHEr TwO wErE wEaTHErEd), CONsIsTs Of sLIGHTLy mOrE THaN ONE aNd a HaLf wHOrLs, raTHEr maTTE; R1 CONsIsTs Of 1.5 wHOrLs, rEGULarLy, dENsELy rIbbEd wITHOUT aNy sIGNs Of spIraL LINEs; rIbs bECOmING sLIGHTLy mOrE wIdELy-spaCEd TOwards ENd Of R1; TraNsITION bETwEEN R1 aNd R2 sUddEN, CLEarLy vIsIbLE, R2 ExTrEmELy dENsELy rIbbEd (FIGUrEs 17A–B); rIbs vEry LOw, NOT TypICaL TO Dicharax; CrOss sECTIONaL vIEw Of R2 rIbs COULd NOT bE ExamINEd, bUT prObabLy sImILar TO THaT Of D. immaculatus n. sp.; EvEry fIfTH rIbLET ELEvaTEd aNd sHarp INsIdE UmbILICUs; LENGTH Of R2 aNd R3 vEry sLIGHTLy mOrE THaN a qUarTEr Of wHOrL COmbINEd; THEy arE Of abOUT THE samE LENGTH; TraNsITION bETwEEN R2 aNd R3 raTHEr CLEarLy vIsIbLE, INdICaTEd by a CONsTrICTION; R3 wITH bLUNT swELLING; rIb dENsITy ON R3 Is sImILar TO THaT Of R2, bUT rIbs LEss rEGULar; apErTUrE aLmOsT ExaCTLy rOUNdEd; OUTEr LIp sHarp, vEry sLIGHTLy rEfLECTEd; INNEr LIp sLIGHTLy THICkENEd, dIsTaNCE bETwEEN THE TwO LIp NOrmaL.

Measurements (in mm). D = 3.8, H = 2.2 (N = 1, LECTOTypE).

Operculum. THE INNEr sUrfaCE COULd NOT bE ExamINEd. THE OUTEr sUrfaCE Is NEarLy smOOTH, bUT THE mULTIspIraL CHaraCTEr Is vIsIbLE.

Variation in specimens. ONLy THE LECTOTypE was IN pErfECT CONdITION, THErEfOrE THE varIabILITy wITHIN spECIEs rEmaINEd UNkNOwN.

Differential diagnosis. Dicharax fargesianus CaN bE dIsTINGUIsHEd frOm aLL CHINEsE aNd VIETNamEsE CONGENErs by THE vEry LOw, rEGULar rIbs ON R2. BEsIdEs THE fINE mOrpHOLOGy Of THE R2 rIbs, D. fargesianus Has sHOrTEr R2+R3 THaN mOsT pOpULaTIONs Of D. cristatus, aNd ITs swELLING ON THE R3 Is UsUaLLy bLUNTEr THaN THaT Of THE OTHEr spECIEs. Dicharax diminutus Is smaLLEr THaN D. fargesianus aNd Has a COmparaTIvELy LarGEr apErTUrE. Dicharax plicilabris Is aLsO smaLLEr aNd fLaTTEr, aNd Has a CrENULaTEd pErIsTOmE, wHICH Is rOUNdEd IN D. fargesianus. SEE aLsO UNdEr D. alticola n. sp. aNd D. immaculatus n. sp.

Distribution. Dicharax fargesianus Is kNOwN ONLy frOm THE TypE sErIEs frOm THE TypE LOCaLITy (FIGUrE 7.).