Page:Walcott Cambrian Geology and Paleontology II.djvu/282



The description of Molaria is outlined in that of the type species.

Genotype.—Molaria spinifera, new species.

Stratigraphic range.—The stratigraphic range is limited to a thin layer of dark siliceous shale about 2 inches in thickness forming the base of the phyllopod bed of the Burgess shale member of the Stephen formation.

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.

The generic name is derived from Molar, the name of one of the mountain peaks east of the "Valley of the Ten Peaks," south of Laggan, Alberta, Canada.

The family reference is tentative.

The dorsal test, when flattened on the shale and viewed from above, is elongate-oval in outline with a long, slender telson; it is obscurely trilobed longitudinally. Surface slightly roughened by minute shallow punctæ. Cephalic shield semicircular in outline, moderately convex. It is divided into a central area with a conical outline corresponding to the glabella of the trilobite and three transverse lobes are indicated by short furrows on each side. Postero-lateral angles without genal spines.

The examination of over 20 specimens has failed to reveal any traces of an eye on the cephalic shield. This might escape observation, but from the close relation of this species to the species in the genus Habelia it is probable that the eyes were pedunculated and beneath the rim of the cephalic shield.

Thorax with eight transverse segments divided into a median and two lateral lobes. The form and arrangement of the segments is clearly shown by figure 2. Abdomen with one long segment and a slender, spine-like telson.

Appendages.—The appendages of the head are not satisfactorily preserved. In one (fig. 5) a pair of short, jointed antennules (a') may be traced by their impression on the test to where they extend beyond the rim of the cephalic shield. On the left a larger and longer appendage may possibly represent an antenna. Several specimens show slender jointed appendages projecting from beneath the