Page:Smithsonian Miscellaneous Collections, Volume 85.djvu/113

Rh splendens (see restorations). The presence of a rudimentary endopodite is suggested on some specimens by an elongate, triangular, light-colored space on the proximal portion of the exopodites as shown by figure 3, plate 20; these light areas may be the outline of a space inside the broad arm of the exopodite, but they usually cross the axis of the arm diagonally; if they do represent the endopodite they were exceedingly delicate and attached by a broad base beside the exopodite in such a manner as to be held almost rigidly in place, and they are always in the fossil state pressed against the proximal section of the exopodite, and they have a silvery sheen so characteristic of the contents of the inside of the limbs of all crustaceans of the Burgess shale preserving the limbs. I do not think that they represent the endopodites, but they are the only suggestion of the latter thus far observed in connection with the abdominal limbs of Waptia.



a, antennae; a.o., anal opening; c, carapace; c.f., caudal furca; e, eye; ex, exopodite; h.c., hepatic caeca; i, intestine; r.p., rostral plate; st, stomach; th.l., thoracic leg.

(✕ 3.) Diagrammatic side view of a section of the animal, illustrating the appendages, digestive tract, etc.

Functions of appendages.—The functions of the antennules and antennae were presumably sensory as in recent Malacostracans, as they do not appear to have been modified for any other purpose, and the proximal joint, as far as known, did not function as a manducatory organ.

The mandibles, maxillulae, and maxillae are unknown; the five pairs of thoracic limbs may have been used for crawling on the bottom, but with short joints and spinous distal joint they could not have been very effective; the exopodites of the eight pairs of abdominal limbs served as natatory organs and also as branchiae, the long delicate filaments presenting an extended surface area to the water.

Digestive organs.—What is known of the digestive system of Waptia indicates that it was somewhat similar to that of the living