Page:Walcott Cambrian Geology and Paleontology II.djvu/267

 to the genus. All that is known of its appendages is shown by figure 4. A number of specimens of the valves in the collection average 5 to 8 mm. in length.

Formation and locality.—Middle Cambrian: (35k) Burgess shale member of the Stephen formation, on the west slope of the ridge between Mount Field and Wapta Peak, one mile (1.6 km.) northeast of Burgess Pass, above Field, British Columbia.

This form differs in the form of the carapace from H. perfecta, as may be seen by comparing figures 1-3, plate 32, with figure 1, plate 31.

Formation and locality.—Middle Cambrian: (35k) Burgess shale member of the Stephen formation, on the west slope of the ridge between Mount Field and Wapta Peak, one mile (1.6 km.) northeast of Burgess Pass, above Field, British Columbia.

The outline of a valve of the carapace is illustrated by figure 5, which is 15 mm. in length. A laterally compressed carapace and abdomen are represented by figure 6. These two figures illustrate all that is known of the species.

Formation amd locality.—Middle Cambrian: (35k) Burgess shale member of the Stephen formation, on the west slope of the ridge between Mount Field and Wapta Peak, one mile (1.6 km.) northeast of Burgess Pass, above Field, British Columbia.

This small species is represented by two specimens. At first it was placed with H. ? circularis (pl. 32, fig. 4), but later it was found to differ in its appendages. The specimen illustrated by figure 7 has the carapace crushed down so as to appear broad oval in outline, but another specimen has a nearly straight dorsal margin. The abdomen is pushed over on to the carapace. The antennæ project from the left side.

Formation and locality.—Middle Cambrian: (35k) Burgess shale member of the Stephen formation, on the west slope of the ridge between Mount Field and Wapta Peak, one mile (1.6 km.) northeast of Burgess Pass, above Field, British Columbia.