148 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 57 



PLATES PAGE 



Plate 24. Ncolenus serratus, Ptychoparia cordillerce, Mollisonia sym- 

 metrica, Tontoia kwaguntensis, Mollisonia gracilis, and 

 Mollisonia ? rara 208 



25. Marrella splendens 210 



26. Marrella splendens 212 



27. Burgessia bella, Waptia fieldensis, and Opabinia regalis 214 



28. Opabinia regalis, Nathorstia transitans, and Naraoia compacta. 216 



29. Molaria spinifera, Habelia optata, Yohoia tenuis, and Yohoia 



plena 218 



30. Bidentia difflcilis, Emeraldella brocki, and Burgessia bella.... 220 



31. Hymenocaris perfecta and Leanchoilia superlata 222 



32. Hymenocaris obliqua, Hymenocaris ? circularis, Hymenocaris 



ovalis, Hymenocaris ? parva, Fieldia lanceolata, and Hurdia 

 victoria 224 



33. Carnarvonia venosa and Tuzoia retifera 226 



34. Hurdia iriangulata, Odaraia alata. and Anomalocaris gigantea. 228 



INTRODUCTION 



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 g-enera of the Merostomata,^ 

 Sidneyia and Amiella; the second, the holothurians and medusae, 

 and the third the annelids.^ 



This paper includes all of the crustaceans of the subclasses Bran- 

 chiopoda, Malacostraca, and Merostomata that occur in the collec- 

 tions of 1909 and 1910. A brief note is also given of some new fea- 

 tures 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 Medusae, also the text references to 

 Lankester's Treatise on Zoology, 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 dis- 

 cusses the theoretical ancestor of the echinoderm.'' Doctor Bather 



' Smithsonian Misc. Coll., Vol. 57, No. 2, 1911, pp. 17-40, pls. 2-7. 

 ' Idem, No. 3, pp. 41-68, pis. 8-13, and No. 5, pp. 109-144, pis. 18-23. 

 'Idem, No. 3. PP- 43-45- 



^What is an Echinoderm? Journal of the City of London College Science 

 Society, Vol. 8, 1901, pp. 1-25. 



