Page:Walcott Cambrian Geology and Paleontology II.djvu/230



This is the fourth preliminary paper based on collections from the Burgess shale member of the Stephen formation in British Columbia. The first paper described two genera of the Merostomata, Sidneyia and Amiella; the second, the holothurians and medusæ, and the third the annelids.

This paper includes all of the crustaceans of the subclasses Branchiopoda, Malacostraca, and Merostomata that occur in the collections of 1909 and 1910. A brief note is also given of some new features in the appendages of the Trilobita, and a few unusual forms of trilobites are noted by brief descriptions and simple illustrations. The few traces of the Ostracoda will not be noticed, and many details of structure of species are omitted, both in description and illustration, as I am planning to follow these preliminary notes with a paper on the Burgess shale fauna that shall include the results of a study of the present collections and those of the field seasons of 1911-1912.

Correction.—By oversight figures 2-4 of my paper on Middle Cambrian Holothurians and Medusæ, also the text references to Lankester's Treatise on Zoölogy, were credited to Lankester instead of to F. A. Bather, the author of the section on the Echinodermata. Doctor Bather calls my attention to a paper by him in which he discusses the theoretical ancestor of the echinoderm. Doctor Bather