PLATE 6.
All figures except 4 and 5, from photographs by C. E. Beecher.
Fig. 1. Triarthrus becki. Specimen 203. A well preserved small individual, showing the appendages of the right side of the thorax. × 11.46.
Fig. 2. Triarthrus becki. Specimen 209. A well preserved individual, showing the antennules and some appendages of thorax and pygidium. For detail of the pygidium, see [pl. 5, fig. 1]. × 4.
Fig. 3. Triarthrus becki. Specimen 218. Ventral side of the pygidium and greater part of the thorax of an individual of medium size. Note especially the relation of exopodites to endopodites of the last two thoracic segments. A drawing of these appendages is shown on text [fig. 43]. × 4,3.
Figs. 4 and 5. Endopodites, probably from a species of Calymene. These specimens, with several others, are on a small slab of limestone from the Point Pleasant (Trenton) beds opposite Cincinnati, Ohio. Specimen in the U. S. National Museum. Photographs by R. S. Bassler.