Page:Walcott Cambrian Geology and Paleontology II.djvu/284

 Geographic distribution.—On the slope of the ridge between Wapta Peak and Mount Field, north of Burgess Pass, and about 3800 feet above Field on the line of the Canadian Pacific Railway, British Columbia, Canada.

Observations.—The generic name is derived from the name Habel as applied to a mountain peak near Wapta glacier at the head of Yoho Valley, British Columbia, Canada.

In form the body of this species resembles Yohoia tenuis, but its long slender telson and thoracic appendages quickly separate it.

The test of the head is finely punctate, and crenulated with minute short spines on the margin. There are eleven body segments bearing appendages that are of nearly uniform size, one smaller abdominal segment without appendages, and the slender telson.

The eye has not been observed in any of the four specimens preserving the head.

Appendages.—On one specimen six slender jointed appendages project forward from beneath the carapace; the posterior of these is a little larger than the others. They represent, in front at least, the first five pairs of appendages of the head. Another specimen shows two slender jointed antennules and posterior to (below) them two larger jointed antennæ with delicate spines extending forward; another antenna is indicated by a small jointed leg-like appendage. The thoracic appendages are somewhat difficult to interpret. One specimen shows the broad terminal joint on eight legs, with traces of it on the three anterior legs; another specimen has five long, slender, jointed legs with a sixth posterior to them that is not over one-half as long; back of the latter there are five of the short legs with the broad terminal joint. The five anterior legs have a rather large gill attached to a short exopodite (?).

The terminal joints of the posterior legs have almost the outline of the pleuron of the segments of the thorax; they gently curve from a broad base to a fine point and have five or more short sharp spines on the anterior margin and somewhat finer spines on the posterior margin; their function was probably natatory.

Surface.—The surface of the head test and tergite of the segments is finely punctate. The telson appears to have been longitudinally striate or smooth.

Dimensions.—The largest specimen has a length of 22 mm. exclusive of the long telson, which is about as long as the body.

Observations.—The presence of this species in the collection was