Taxonomic report on some monstrilloids (Copepoda, Monstrilloida) from southeast Mexico with the description of a new species of Monstrilla

During zooplankton surveys carried out between 1987 and 1991 oV the norther n coast of the Yucatan Peninsula, southeast Mexico, several monstrilloid co pepods were collect ed. Three species were identified: Cymbasoma chelemense Suarez-Morales and Escamilla, 1997, C. quintanarooense (Suarez-Morales, 19 94) and a new species of Monstrilla. Cymbasoma quintanarooense was describe d from the western Caribbean Sea a few years ago; new and complementary mor phological dat a are added to the original description of this species. Pre vious to this survey, only one specimen of Cymbasoma chelemense, the holoty pe, had been collect ed; an additional specimen is recorded here from the t ype locality for this species. Monstrilla humesi sp. nov. is described foll owing a set of recent ly proposed standards for the description of monstril loid copepods. The new species is quite similar to M. helgolandica Claus, 1 863 and to M. gracilicauda Giesbrecht, 1892a. It can be distinguished by th e presence of a bilobed fifth leg, the position of the oral papilla, and by the proportional length of its genital compound somite.