| A comparison of the skeleton of a successive thoracic segment in various Malacostraca shows the development and growing complexity of phragmal structure. It first appears in some Mysicacea and in Euphausiacea by means of an interarthrodial lamina issued from sternite. In Decapoda, Penaidae, Atyidae, Processidae, Palaemonidae, this lamina is diversified and some elements from pleural origin join it. The beginning of the so constituted wall considerably increases in Nephropidae and becomes ramified. |
