20 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 85 



Functions of appendages.— The functions of the cephalic and 

 thoracic Hmbs were probably similar to the functions of those of 

 Marrella splendens. 



Mode of occiirreyice. — This delicate and beautiful little crustacean 

 occurs abundantly in association with Marrella splendens and Waptia 

 fleldensis, and is quickly recognized, even when distorted and crushed, 

 by its carapace and strongly marked hepatic caeca. The carapace is 

 almost always outlined on the shale, as are frequently the body and 

 telson ; the large strong endopodites are usually more or less clearly 

 marked, although their jointed structure has generally been lost in the 

 flattening in the shale ; the exopodites were so delicate that they are 

 rarely preserved, and the same is true of the labrum and eyes. 



Comparison ivith crustaceans. — Biirgessia has certain characters in 

 common with Marrella and Naraoia and belongs in a group with them 

 which will be discussed later (p. 37). 



Diagrammatic restorations of ventral surface. — I have endeavored 

 to present, in text figures 3, 4, and 5, interpretations of the structure 

 of my Burgessia hella. 



Plesiotypcs. — U. S. N. M., Nos. 839473-0. 



WAPTIA Walcott 1912 



WAPTIA FIELDENSIS Walcott 



Plate 18, figs. 2-5 ; plate 19; plate 20; plate 21, fig. 2 



Waptia fleldensis Walcott, 1912, Smithsonian Misc. Coll., vol. 57, no. 6, 1912, 

 p. 181, pi. 27, figs. 4, 5. 



The general characters of this species were described in 191 2, since 

 when a large number of specimens have been collected from the Bur- 

 gess shale, a few affording data from which a fairly accurate dia- 

 grammatic restoration of the animal may be drawn (text fig. 6). 



Exoskeleton.- — -The exoskeleton of the carapace, trunk, and caudal 

 furca was very thin and readily distorted. The trunk consists of 5 to 7 

 short cephalic segments ; 8 narrow thoracic segments, each bearing a 

 pair of uniramous appendages ; 6 long abdominal segments and 2 

 broad lobelike terminal caudal furca or rami ; the latter have three 

 transverse lines indicating four fused segments. The posterior margin 

 of the abdominal segments bears four or more strong spines with a 

 fringe of small, short, sharp spines between them. The last or anal 

 segment has a minute anal opening on a slightly rounded elevation 

 near its posterior ventral margin. The abdominal segments have often 

 been narrowed and lengthened, or broadened and shortened by dis- 

 tortion in the shale. 



