Page:Walcott Cambrian Geology and Paleontology II.djvu/178

112 As in the case of the holothurians the annehds go to prove that the Cambrian fauna was highly developed and differentiated in pre-Cambrian Lipalian time.

Chætognatha allied by external form to Sagitta. Body divided into a head, trunk, and tail. One pair of lateral fins. An interior septum occurs between the head and body, but none is shown between the body and tail.

One genus, Amiskwia.

As there is but one species the generic and specific descriptions will be combined under the species.

Genotype.—Amiskwna sagittiformis, new species.

Stratigraphic range.—The stratigraphic range is limited to a band of dark siliceous shale about 4 feet in thickness forming a part 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.

Observations.—Amiskwia resembles Sagitta superficially, but differs from the latter genus in the form of the head, the presence of strong tentacles, the absence of a hood about the head, the strong single pair of lateral fins, and the absence of a posterior septum.

Generic name derived from Amiskwi, name of a river west of Mount Burgess, British Columbia, Canada.

Body cylindrical and divided into a broadly elongate oval head, a cylindrical body, and an expanded tail. The head, expanding from the neck, contracts to a bluntly pointed anterior end, from the rounded angles of which project a pair of strong tentacles. The lateral fins of the body are a little more than one-third the length of