(formerly round) filament, which is beautifully preserved in some specimens (fig. 8, pl. 22). The fringe of filaments often overlap those of the adjoining exopodite so as to form an imbricating series of fringes the entire length of the body.
An exopodite 3 mm. in length has attached to it 42 filaments that average about 12 to 14 to the millimeter in the proximal portion, and 14 to 16 towards the distal end; they increase gradually in length from the proximal end until on the distal section they may be as long as the entire exopodite. A rusty specimen laid aside as of little value proved on cleaning to have the filaments preserved as long, slender cylinders or tubes (see fig. 8, pl. 22).
Most of the fossil specimens have the fringes extending forward and outward, but when the animal was living they undoubtedly extended outward and backward so as not to impede its forward movement.
As mentioned under Cephalic appendages, there is good reason to think that the two posterior oral appendages (maxillulae and maxillae) have in addition to the simple jointed endopodite an exopodite similar in structure to that of the thoracic limbs.
Epipodite.—A single specimen shows what I thought in 1912 to be a large epipodite or branchiae,[1] but which I have now decided to be several of the fringed exopodites pressed down together and more or less macerated in the contents of the body which were squeezed out on that side. It was only after finding a number of examples showing the fringed exopodites arranged in this manner but not pressed into each other that I gave up the view that a large epipodite was present.
Several specimens have been found since 1912 that indicate the presence of a small oval flattened lobe attached to the dorsal side of the protopodite, or it may be to the proximal joint of the exopodite, but it may be that this appearance is caused by the manner in which the protopodite and the segments of the body are matted down together; some of the thin oval bodies, however, are so clearly defined that they suggest the presence of a small epipodite, but I do not consider the evidence sufficient to warrant representing them on the restoration of the thoracic limb.
Functions of appendages.—The proximal joints of the antennae may have assisted in mastication and may have had a sensory function. The proximal joints of the mandibles undoubtedly served in mastication, but whether those of the slender leglike maxillulae and maxillae aided is undetermined, as nothing has been seen of either
- ↑ Smithsonian Misc. Coll., vol. 67, pls. 29, 32, 1918.
