The appendages of the head consist of two pairs of antennæ, and three pairs of slender, jointed legs. Both pairs of antennæ are slender and many-jointed, the antennules somewhat smaller than the antennæ. The exact structure of the limbs about the mouth has not yet been made out, but they are slender, tapering, endopodite-like legs, with at least three or four segments in each, and probably more. There are eight pairs of thoracic appendages, each limb having the form of the endopodite of a trilobite and consisting of seven segments and a terminal spine. The proximal three segments of each appendage are larger than the outer ones, and have a flattened triangular expansion on the inner side. Walcott also states that "One specimen shows on seven pairs of legs, small, elongate, oval bodies attached near the first joint to the outer side of the leg. These bodies left but slight impression on the rock and are rarely seen. They appear to represent the gills." They are not figured, but taken in connection with the endopodite-like appearance of the segmented limbs, one would expect them to be vestigial exopodites. A small hypostoma is present on the ventral side, and several of the specimens show wonderfully well the form of the alimentary canal and the hepatic cæca. The main branches of the latter enter the mesenteron just behind the fifth pair of cephalic appendages. Behind the thorax the abdomen is long, limbless, and tapers to a point. It is said to consist of at least thirty segments. Compared with _Apus_, _Burgessia_ appears both more primitive and more specialized. The carapace and limbless abdomen are _Apus_-like, but there are very few appendagiferous segments, and the appendages are not at all phyllopodan, but directly comparable with those of trilobites, except, of course, for the uniramous character of the cephalic limbs. A closer comparison may be made with _Marrella_. =Waptia fieldensis= Walcott. Illustrated: Walcott, Smithson. Misc. Coll., vol. 57, 1912, p. 181, pl. 27, figs. 4, 5. The carapace is short, covering the head and the anterior part of the thorax. The latter consists of eight short segments with appendages, while the six abdominal segments, which are similar to those of the thorax, are without limbs except for the last, which bears a pair of broad swimmerets. The eyes are marginal and pedunculate. The antennules are imperfectly known, but apparently short, while the antennas are long and slender, with relatively few, long, segments. The mandibles appear to be like endopodites of trilobites and show at least six segments. As so often happens in these specimens from British Columbia, the preservation of the other appendages is unsatisfactory. As illustrated (Walcott, 1912 A, pl. 27, fig. 5), both endopodites and exopodites appear to be present, and the shaft of the exopodite seems to be segmented as in _Triarthrus_.