Page:Walcott Cambrian Geology and Paleontology II.djvu/182

116 by Mrs. Walcott in splitting a slab of shale that had been slid down the mountain side and carried by pack animal to the Burgess Pass camp. We were all greatly interested and every one was on the alert to find other specimens. About ten days after the anterior half of the specimen represented by figs. 1 and 2 was found Mrs. Walcott called my attention to another "straight worm" she had found in a slab that had been blasted out of the ledge and taken to camp after the first discovery of the long annelid. I compared the two specimens and found that the break across them was on the same angle and that they fitted together to form the entire animal. Part of the second find is shown by fig. 5. The two parts united are 26 cm. in length. Subsequently several fragmentary specimens were found, but nothing equal to the specimen so strangely and fortunately saved by a most unusual combination of circumstances.

There are a number of unsolved questions relating to this annelid on which I will not now speculate, as the collection of 1911 may give further material for study.

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

Polychæta with a slender fusiform body with many segments, large, strong, segmented parapodia attached to alternating groups of segments, setæ on parapodia as hoops or jointed spines. Head small with two and probably four tentacles.

Observations.—It would be hazardous to define a family of living Polychæta from the data afforded by Aysheaia pedunculata, but it would be still more so to identify this strongly marked form with any of the described families. The peculiar segmentation of the body and the attachment of the large parapodia on alternating groups of segments are unusual. While it is not impossible, it is not probable that a Cambrian annelid of this type would belong to any of the families of recent annelids.

Of this genus there is but one species and one specimen known. The generic and specific descriptions are combined under the species.

Genotype.—Aysheaia pedunculata, new species.