INTRODUCTION
It is obvious that one person cannot cover, even in a very cursory manner, the entire field of Cambrian stratigraphy and paleontology, especially with such rich faunas as the Burgess shale extant. Again, in the case of the Burgess shale faunas, none but a trained student in biology can do more than merely assign specific and generic names to the gross forms. Further, it is doubtful if any biologist, however versatile, could by long years of study perceive everything to be learned from these wonderful fossils. In view of these facts it has seemed advisable to encourage specialists to study the various classes represented rather than attempt to monograph the subject as a whole. Accordingly, such a study by Dr. G. E. Hutchinson has recently been printed[1] and one by Dr. Rudolf Ruedemann has been submitted for publication.[2] In this way we may hope to carry on the work suspended by the passing of the discoverer of these unique forms.
The following descriptions either were prepared entirely by Doctor Walcott or are based on notes and illustrations left by him.
Formation and locality.—For every species described in this paper, the formation and locality are as follows: Middle Cambrian, Burgess shale: (Loc. 35k) on the west slope of the ridge between Mount Field and Wapta Peak, 1 mile (1.6 km.) northeast of Burgess Pass, near Field, British Columbia.
DESCRIPTION OF GENERA AND SPECIES
MARGARETIA, new genus
The characters of this strange organism are presented in the specific description or shown in the illustrations.
Genotype.—M. dorus, new species.
MARGARETIA DORUS, new species
Plate 1, figs. 1-6
More than 70 specimens of this peculiar organism have been assembled from the Burgess shale collections. In the following description comparisons are made with algae. Other notes by Doctor Walcott, apparently his latest, together with suggestions by Mr. A. H. Clark, and particularly the presence in the same drawer of specimens of Titanideum suberosum, indicate that Doctor Walcott's latest opinion was that M. dorus might really be an Alcyonarian.
Description.—Mass forming a thin membranous perforated sheet, narrow at the base and expanding to a width of 1.5 cm. in 2 cm. distance; length of narrow base about 1.5 cm. and of wider portion 4 cm.; the perforations are elongate oval and apparently arranged on longitudinal and obliquely transverse lines; tegument presumably
