A new species of Alteutha Baird (Harpacticoida: Peltidiidae) from north-western Mexico

As an effort towards improving our knowledge of the Mexican harpacticoid fauna, new species and new records of different families have been published during the last 14 years. The material presented herein belongs to a group of species of Alteutha characterized by the lack of inner armature in P2-P4 EXP1. The new species herein presented seems to be related to Alteutha rara Jakobi and A. oblonga (Goodsir). It resembles A. oblonga from Norway and Argentina given the armature of the A2 EXP and armature of P1 EXP2, but differs from the Norwegian form in the position of the lateral seta of the first endite of the maxilla and in the P1 EXP:ENP length ratio. The Mexican species matches the written description of the Argentinean specimens, but no conclusive comparisons could be made regarding the P1 EXP:ENP length ratio, the relative position of the setae/spines of bucal appendages and swimming legs.