8 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 76 



Whether the imperfect specimen illustrated on Plate 4, Figure 3, 

 really should be regarded as belonging to this species can not be 

 decided with certainty because of its incompleteness, but a careful 

 study of it indicates that it likely does. 



Horizon and locality. — Middle Cambrian, Burgess shale ; (loc. 35k) 

 near field, British Columbia. 



TUZOIA BURGESSENSIS, new species 



Plate 2, figure 1 ; Plate 3, figure 1 



Comparing this species with T. retifera we first note that it is 

 longer and narrower and that the reticulations of the keel appear to 

 be more numerous and stronger. The posterior marginal spines are 

 about the same in both species but the small spines are larger and 

 more regular both in size and spacing than in the genotype. Those 

 of intermediate size appear to be absent. This species also has sev- 

 eral blunt spines along the dorsal line the extensions of which are 

 not as long or slender as in T. retifera. 



Horizon and locality. — Middle Cambrian, Burgess shale; (loc. 35k) 

 near Field, British Columbia. 



Holotype and paratype.—C?it. No. 80477, U.S.N.M. 



TUZOIA CANADENSIS, new species 



Plate 2. figures 2, 3 



This second new species determinable in the Burgess shale material 

 on hand is represented by only three or four fragmentary specimens, 

 yet its specific characters may readily be seen. 



Since the general shape and character of the reticulations of this 

 species do not differ materially from the same features in both of the 

 foregoing species its right to specific rank rests on others. The 

 most prominent of these is the possession of four instead .of three 

 posterior spines which are longer and slenderer than in the preceding 

 species and they are followed anteriorly by perhaps twelve or more of 

 intermediate size, widely and evenly spaced along the margin, end- 

 ing with one situated forward of the keel. Between these large and 

 intermediate spines the usual small ones occur, in this case being 

 most like those in T. retifera. The spines along the dorsal line are 

 also longer and more slender, and perhaps more numerous than in 

 T. hurgessensis. 



Horizon and locality. — Middle Cambrian, Burgess shale ; (loc. 35k) 

 near Field, British Columbia. 



Holotype and paratype. — Cat. No. 80478, U.S.N.M. 



