Page:Smithsonian Miscellaneous Collections, Volume 85.djvu/122

Rh strong mandibles and the thoracic limbs. In figure 1, plate 22, their exopodites are shown on the left side, and on the right side the endopodites of the maxilla with the exopodite of the maxillula, the endopodite of the latter having apparently been pushed under and a little forward of the mandible. Sometimes the endopodite is present but the joints are indistinguishable or only a few can be seen.

Thoracic limbs.—The biramous thoracic limbs appear to be uniform in character from the cephalon to the minute plate-like telson at the posterior end of the body. Each limb is formed of a protopodite, a jointed endopodite, and a jointed fringed exopodite.

Protopodite. —The large protopodite is attached by its inner end to the lower side of the body segment about half way between the

10.—Diagrammatic outline of the posterior side of one of the anterior thoracic limbs: pr, protopodite; en, endopodite; ex, exopodite; f, filaments of exopodite: i, intestine.

This figure indicates the point of attachment of the limb to the body, also approximate position of the intestine.

ventral median line and the rounded outer side of the body apparently in the same manner as the trunk limbs of Apus, except that in the latter there is no evidence that the protopodite served as a gnathobase. The protopodite is elongate, apparently cylindrical at its inner end, and flattened somewhat at the distal end; it is strong, and supports an endopodite and an exopodite. It is usually flattened so as to appear of about the same width throughout its length; a few specimens indicate that it narrowed at its proximal end, essentially as shown in the restoration.

Endopodites.—The endopodite or leg is formed of six joints. The first five joints of the anterior limbs are rather flat and broad at the