Morphological Observation of Museum Specimens of Astacus astacus and Pontastacus leptodactylus

Both external and internal morphological characteristics (the gastric mill and the gill on maxillipeds) of museum specimens of European Astacidae, namely Astacus astacus and Pontastacus leptodactylus, were observed and detailed illustrations and descriptions are herein provided. Several morphological variations in external morphology were detected, and the characters to discriminate between Astacus and Pontastacus have been used to update the diagnoses of these two genera.