Page:Smithsonian Miscellaneous Collections, Volume 85.djvu/121

Rh Cephalic appendages.—These consist of antennae, mandibles, simple slender maxillulae, and slender maxillae. The proximal joints of the cephalic appendages are so badly crushed and matted together beneath the labrum or just back of it that it has been very difficult to determine exactly their form and relations to each other, but it is highly probable that they were arranged as in the restoration (text fig. 9).

Antennae.—The antennae are long, slender, and many-jointed, with fine spines at the distal end of each joint. As far as may be determined, the proximal joint was attached to the ventral surface beneath the postero-lateral angle of the labrum just in advance of the mandible. There is no evidence that it served as a jaw or manducatory organ except that in specimens preserving them their inner (proximal) end is in front of and adjoining the large proximal joint of the mandibles (see figs. 3, 6, and 7, pl. 22).

Mandibles.—The mandibles are formed of a strong proximal joint with four short, strong joints followed by five slender, elongate joints (see fig. 9), the latter being almost covered with very fine setae that give a plumose appearance to the appendage as it extends out beyond the great backward curving spines of the carapace. I examined hundreds of specimens before finding a proximal joint with its inner end sufficiently well preserved to suggest the character of its masticatory surface; two specimens indicate that it is as shown in figure 7, plate 22, and in the restoration. There is no evidence as to whether the proximal joint is composed of one long joint or two closely united short joints. The usual location of the mandibles in well preserved specimens is shown by figures 1 and 2, plate 22.

Maxillulae.—These are long, slender, and with about 10 slender joints. They look like thoracic legs (endopodite) but their position and slender joints serve to distinguish them. Portions of them may be seen in figures 1 and 2, plate 22.

Maxillae.—As far as known the maxillae are formed of joints a little longer than those of the maxillula and about the same diameter; both appear to have been slender, rather closely jointed, simple appendages as far as the endopodite was concerned; there is strong evidence that an exopodite was present, similar to those of the exopodites of the trunk appendages, but they have not been seen directly attached to the protopodite; where the parting of the shale is on the plane of the exopodites they are usually present next to the mandible and directly over the position of the maxillulae and maxillae, which suggests strongly that they were present.

The maxillulae and maxillae were so slender that they are usually absent as the result of having been torn off or crushed between the 3