TWOSYMP ATRICSPECIES OF AXIUS FROMTHE NORTH-WEST ATLANTIC(DECAPODA, THALASSINIDEA, AXIIDAE) BY BRIAN KENSLEY 1/ Departmentof SystematicBiology, National Museum of NaturalHistory, Smithsonian Institution, Washington,D.C. 20560,U.S.A. ABSTRACT Axiusserratus Stimpson,1852, is redescribed and illustrated, and its distribution based on 54 recordsof 68 specimensis recorded. The sympatric, and rarely recorded Axiusarmatus Smith,1881, isredescribed and illustrated for the rsttime, based on six female specimens from veseparate records.These two species are compared with the eastern Atlantic Axiusstirhynchus Leach,1815. Thethree species can be separated on the basis of the uropodal transverse suture, telsonic and pereopodalspination, and pereopod 4 sternitestructure. RÉSUMÉ Axiusserratus Stimpson,1852 est redé crit et illustréet saré partition gé ographique est donné e, àpartirde 54 signalements de 68 spé cimens. L ’espèce sympatrique Axiusarmatus Smith,1881, rarementrencontré e, est redé crite et illustrée pourla premiè re fois, à partirde sixindividus femelles provenantde cinq stations sé paré es. Ces deux espè ces sont comparé es avec Axiusstirhynchus Leach, 1815,de l’ Atlantiqueoriental. Les trois espè ces peuvent ê trediffé rencié es par la suture transversale del’uropode, les é pinesdu telsonet des pé ré iopodes et en n lastructuredu sternitedu pé ré iopode 4. INTRODUCTION Thegeminate species Axius serratus Stimpson,1852, in the north-western Atlantic, and Axius stirhynchus Leach,1815, in the north-easternAtlantic, are bothlong-established, fairly frequentlyrecorded species. Thata third species of Axius occursin the western NorthAtlantic is oftenoverlooked. In fact, Axius armatus Smith, 1881,has onlybeen mentioned three times in the literature since its description,and has neverbeen illustrated. Thelast mention(Sakai &De Saint Laurent,1989) questioned its positionin the genus Axius.Sixspecimens 1/ e-mail:[email protected] c KoninklijkeBrill NV ,Leiden,2001 Crustaceana 74(9):951-962 ° 952 BRIAN KENSLEY (all females) ofthis species havebeen deposited in the collections ofthe National Museumof Natural History,includingone of Smith’ s syntypes.It was thought useful to ll this gapin the knowledgeof the east coast U.S.shelf fauna,and to describe andillustrate the twowestern NorthAtlantic species, anddocument their distribution. Theholdings of A. serratus in the SmithsonianInstitution, as well as those ofthe Museumof ComparativeZoology, Harvard (most ofwhich were collected byvarious NOAA National Marine Fisheries Service programs)were examined,on the off-chancethat specimens ofthe apparentlyrare A. armatus had beenmisidenti ed. Unfortunately, no furtherspecimens werefound. Abbreviations:cl, carapacelength (posterior orbital marginto posterior cara- pacemargin); MCZ,Museum of Comparative Zoology, Harvard University; NOAA,National Oceanicand Atmospheric Agency; USNM, United States Na- tional Museum,Smithsonian Institution; VIMS,Virginia Institute ofMarine Sci- ences. SYSTEMATICS Axius armatus Smith, 1881( gs. 1, 2,4) Axiusarmatus Smith,1881: 433; De Man, 1925: 3, 9,11. ?Calocaride Sakai& DeSaint Laurent, 1989: 101. Materialexamined. — Syntype,USNM 35391, cl13.2 mm (eggspresent in ovaries), R/ V“Fish Hawk”sta. 878, off Martha’ s Vineyard,Massachusetts, 39 ±550N 70±5401500W,260m, 13 September 1880.— USNM 174450,ovigerous cl8.1mm (damaged),off South Carolina, 32 ±300N 78±290W, 218m, coll. K. Shaw,6 June1978. — USNM 174451, cl6.2 mm, offSouth Carolina, 32 ±300N 78±290W,218m, coll. K. Shaw,6June1978. — USNM 243489,2 cl5.6mm, 6.9mm, R/V“Fish Hawk”sta. 949, off Martha’ s Vineyard,Massachusetts, 40 ±030N 70±310W,183m, 23 August 1881. —USNM 306381, cl7.0 mm, George’s Bank,40 ±2201200N 68±3001200W,108m, R/ V“Oceanus” cruiseM10, sta. 12, 13 November1983. Description.— Female syntype.Carapace ( gs. 1A, B, 2A) with rostrum reachingto distal edgeof antennularpeduncle article 2,armedwith 3to 6teeth (4in 3specimens), posteriormost in supraocularposition, but not enlarged, rostral marginproduced posteriorly as nelateral carina; submediancarina aneridge anteriorly recurved,lacking teeth; mediancarina bearing2 or3 teeth (3in one specimen),unarmed posterior to tubercle.Sternal plate betweenbases ofpereopods 4(g. 2C) with lateral angerounded. Abdominal pleura ( g. 1C) ventrally broadlyrounded, that ofabdominal somite 2broadest.Telson ( g. 1D)about 1.5 times longerthan basal width; lateral margins with 4serrations, posterior margin convex,with small spine at midpoint;dorsal surface with 3spines onleft half,2 on right..