AKT. 9 NEW CAMBRIAN CRUSTACEA — RESSER 13 



through HyTnenocaris, Peltocaris^ Ceratocaris.'^^ Thus, while this 



form was classified with Ajms its true position was hinted at from 



the beginning. 



The better preserved Burgess shale specimen allows us to get a 



more complete conception of the major features. 



Genotype. — Protoca/ns nmrshi Walcott. (See pi. 6, figs. 1, 2.) 

 GeograpMo and stratigraphio distribution. — Lower and Middle 



Cambrian. Vermont and British Columbia. 



PROTOCARIS PRETIOSA, new species 



Plate 4, figures 1, 2 



A single Burgess shale specimen preserving the soft body, both 

 within the carapace and the abdominal portion that extended be- 

 yond, apparently belongs to the genus Protocaris. 



Both valves of the carapace are preserved. The left one is flat- 

 tened out evenly, but the right is crushed in an oblique direction. 

 In general shape and the presence and position of a keel, this shell 

 conforms to Tuzoia but both reticulations and marginal spines are 

 lacking. 



It was possible to remove the matrix that had filtered between 

 the carapace and the soft body of the animal within and which 

 preserved an impression of the underside of the left valve, thus 

 exposing the body itself. None of the head parts are well shown, 

 since in flattening the original convexity the anterior portion was 

 crowded together, thereby effacing the delicate structures. Omitting 

 the head parts the remainder of the body is divisible into a thoracic 

 division with numerous segments all limb-bearing, an abdominal 

 portion also composed of many segments which appear to have had 

 much shorter or no appendages and finally a third bifurcated caudal 

 division. This latter has practically the same shape as is Waptia 

 ■fieldensis. 



Comparing this species with the genotype, P. marshi, we can see 

 but few important differences. This new species seems to have the 

 valves more rounded in front, but P. mm'shi is crushed down on the 

 sides and may thereby be somewhat changed from its original out- 

 line. The different aspect of the abdominal portions of the two 

 species is accounted for by the fact that P. marshi was flattened 

 vertically while P. pretiosa suffered pressure at an oblique angle. 



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

 35k) near Field, British Columbia. 



Holotype.—C2it. No. 80483, U.S.N.M. 



RODDYIA, new genus 



While the single specimen on which this genus is based leaves much 

 to be desired, it is so unlike anything else from these beds or that has 



