On the distinctive characters of Talorchestia Brito Stebb. and Talitrus Saltator (Mont.)

The distinction between the genera of the Talitridae is mainly based — at least where the Dutch species are concerned — upon the shape and size of propodite and dactylus of the gnathopods (cf. TESCH: Talorchestia brito etc. in Zoologische Mededeelingen, 's Rijks Museum van Nat. Hist., Leiden, Dl. II, 1916). Intermediate between the genera Talitrus and Orchestia is the remarkable genus Talorchestia, which STEBBING christened with that compound name because the females should be referred to Talitrus, but the males to Orchestia, if we ignored that they belong together. For the second gnathopod of the males carries the huge hand, which distinguishes Orchestia ♂ ♂ from Talitrus ♂ ♂. The females, however, differ from those of Orchestia in that their 1st gnathopod is not feebly subchelate, but simple as in Talitrus. With the males the species can be easily recognized by the typical Talitrus saltator (Mont.) ♀, 2nd gnathopod. form of the propodite of the second gnathopod. With the females this is by no means so easy. In Holland two species of Talorchestia occur, viz., Talorchestia deshayesii Aud. and Talorchestia brito Stebb. T. deshayesii Aud. can be readily distinguished by its smaller size and more slender form. Besides the eyes are comparatively smaller. The female Talorchestia brito Stebb., however, resembles Talitrus ♀ so closely „that they are scarcely if at all to be distinguished from each other." This is quoted from Dr. TESCH, who in 1916 recorded T. brito for the first time as belonging to the Dutch fauna. But in the same paper he hints at the possibility — judging from STEBBING's figures — of find-