2l8 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 57 



DESCRIPTION OF PLATE 29 



PAGE 



Molaria spinifera Walcott 200 



Fig. I. (X3.) Side view in which the thoracic pleurae of the segments 

 have been broken away so as to show appendages. U. S. 

 National Museum, Catalogue No. 57688. 

 2. (X3-) Dorsal view. U. S. National Museum, Catalogue No. 

 57689. 



3- (X3) Ventral view, showing some of the gills (br), liver 



(k) beneath the cephalic shield, and alimentary (al) canal. 

 The ends of the thoracic segments (ths) are marked by fine 

 lines. U. S. National Museum, Catalogue No. 57690. 



4- (X3-) Dorsal view. Minute appendages show from beneath 



abdominal segment, also setiferous joints of the thoracic 

 legs. U. S. National Museum, Catalogue No. 57691. 

 5. (X3) Dorsal view, a' = antennules. U. S. National Museum, 

 Catalogue No. 57692. 



Habelia optata Walcott 202 



Fig. 6. (X2.) Side view of a specimen flattened in the shale. Three 

 of the setiferous legs near the head have been pushed out 

 above the body. U. S. National iMuseum, Catalogue No. 

 57693- 



Yohoia tenuis Walcott 172 



Fig. 7. (X2.) Side view showing the pleurae of the thorax and 

 traces of the appendages of the head. U. S. National Mu- 

 seum, Catalogue No. 57694. 



8. (X3.) Specimen with abdomen and expanded rami forming a 



swimming tail. U. S. Museum, Catalogue No. 57695. 



9. (X2.) Fragment of thorax and head, showing segmentation of 



thorax, eyes, antennule in center and part of a large antenna. 



The latter has its spiniferous terminal joint turned down 



towards the eye on the right side (upper in drawing). U. S. 



National Museum, Catalogue No. 57696. 

 10 and II. (X2.) Small specimens seen from above. U. S. 



National Museum, Catalogue Nos. 57697 and 5769S. 

 12. (X2.) Side view of a specimen showing segmentation of head 



and thorax ; antenna and portions of thoracic appendages. U. 



S. National Museum, Catalogue No. 57699. 

 13- (X3-) The anterior half of figure 12, still further enlarged. 



Yohoia plena Walcott 173 



Fig 14. (X3-) A small specimen showing the general form of the 

 species. Better specimens have been found since the plate 

 was prepared and will be illustrated in a future paper. U. 



S. National Museum, Catalogue No. 57700. 



All of the specimens illustrated on Plate 29 are from locality (35k) Middle 

 Cambrian : Burgess shale member of the Stephen formation, on the west slope 

 of the ridge between Mount Field and Wapta Peak, one mile (1.6 km.) north- 

 east of Burgess Pass, above Field, British Columbia. 



