NO. 3 BURGESS SHALE FOSSILS WALCOTT 2$ 



SKANIA, new genus 



Description. — Dorsal shield thin, broadly rounded in front and 

 tapering from the postero-lateral angles of the cephalic carapace to 

 the posterior end of the shield. 



Cephalic carapace transverse with the postero-lateral angles ex- 

 tended into spines ; posterior margin arched forward ; frontal margin 

 reflected to form a doublure to whicli a small elongate labrum is 

 attached. Eyes unknown but indicated by a bright spot on the carapace 

 a short distance outward from the side of the labruuL No traces of 

 facial sutures. 



Posterior dorsal shield, elongate and formed of 14 or 15 fused 

 segments with a more Or less distinctly marked border. There is a 

 short transverse segment or telson (pygidium) outlined, but whether 

 it is free from the next anterior segment is unknown. 



Surface of test apparently smooth. 



Dimensions. — This genus is based on a small animal, ^S'. fragilis, 

 5 to 17 mm. in length. 



Appendages. — There are indications of antennae, three pairs of 

 cephalic limbs, and a pair of limbs for each segment of the posterior 

 dorsal shield. 



Digestive organs. — An intestine extends from the posterior segment 

 forward to the central part of the cephalic carapace where it widens 

 out to form an elongate oval stomach. There are traces of hepatic 

 caeca adjoining the stomach. 



Genotype. — Skaiiia fragilis Walcott. 



Stratigraphic range. — The stratigraphic range is limited to a band 

 of dark siliceous shale about 4 feet in thickness forming a part of the 

 Burgess shale member of the Stephen formation. 



Observations. — The generic name is derived from Skana, the name 

 of a glacier in the Mount Robson District, Al])erta, Canada. 



The specimens representing the species of this genus are small and 

 so thoroughly flattened in the shale that little more than a black film 

 remains. This makes it very difficult to obtain details and also leaves 

 some doubt as to whether the posterior dorsal shield is formed of 

 fused or free segments.' 



SICANIA FRAGILIS, new species 



Plate 21, fig. I 



Description. — General outline irregularly heart-shaped but subject 

 to wide variation owing to distortion by compression. 



' At the head of these notes, Doctor Walcutt lattr wrote, "A trilobite, 

 C. D. W." 



