The first thoracic limb is uniramous and similar to the maxillæ, but the five following pairs are biramous swimming legs with coxopodite, basipodite, exopodite, and endopodite. Both the exopodite and endopodite are shorter than in the trilobites, but bear setæ and spines. The last pair of thoracic limbs are usually modified in the male into copulatory organs. In some females they are enlarged to form plates for the protection of the eggs, in others they are unmodified. In still others they are much reduced or disappear. The abdomen is without appendages. The development in Copepoda is direct, by the addition posteriorly to the larval form (nauplius) of segments, and the appendages remain nearly unmodified in the adult. Altogether, the primitive Copepoda seem much more closely allied to the Trilobita than any other modern Crustacea, but unfortunately no fossil representative of the subclass has been found. This is not so surprising when one considers the habits and the habitat of most of the existing species. Many are parasitic, many pelagic in both fresh and marine waters, and many of those living on the bottom belong to the deep sea or fresh water. Most free-living forms are minute, and all have thin tests. The eyes of copepods are of interest, in that they suggest the paired ocelli of the Harpedidæ and Trinucleidæ. In the Copepoda there are, in the simplest and typical form of these organs, three ocelli, each supplied with its own nerve from the brain. Two of these are dorsal and look upward, while the third is ventral. In some forms the dorsal ocelli are doubled, so that five in all are present (cf. some species of Harpes with three ocelli on each mound). In some, the cuticle over the dorsal eyes is thickened so as to form a lens, as appears to be the case in the trilobites. These peculiar eyes may be a direct inheritance from the Hypoparia. ARCHICOPEPODA. Professor Schuchert has called my attention to the exceedingly curious little crustacean which Handlirsch (1914) has described from the Triassic of the Vosges. Handlirsch erected a new species, genus, family, and order for this animal, which he considered most closely allied to the copepods, hence the ordinal name. _Euthycarcinus kessleri_, the species in question, was found in a clayey lens in the Voltzia sandstone (Upper Bunter). Associated with the new crustacean were specimens of _Estheria_ only, but in the Voltzia sandstone itself land plants, fresh and brackish water animals, and occasionally, marine animals are found. The clayey lens seems to have been of fresh or brackish water origin.