NO. II NEW LOWER CAMBRIAN SUBFAUNA 315 



direct line north of summit of Robson Peak and northwest of Yellow- 

 head Pass, in western Alberta. Canada. 



CALLAVIA EUCHARIS, new species 

 Plate 53, fig. I 



This fine species is represented by one entire specimen. It has 23 

 segments in the thorax, and a very small and narrow pygidium. The 

 cephalon is very much like that of Callavia perfecta, but the thoracic 

 segments are proportionally narrower and there are six more of 

 them. 



The dorsal shield has a length of 38 mm., with a width of 30 mm. 

 at the back of the cephalon. 



Traces of the surface show it to have been ornamented with a fine 

 network formed of low, sharp ridges such as is found on most species 

 of the JNIesonacidas. 



Formation and locality. — Lower Cambrian : (6ik) Mahto forma- 

 tion ; dark, hard siliceous shale ; northeast base of Mumm Peak above 

 IMural Glacier on west side of Hitka Pass, 6 miles (9.6 km.) in a 

 direct line north of summit of Robson Peak and northwest of Yellow- 

 head Pass, in western Alberta, Canada. 



CALLAVIA PERFECTA, new species 



Plate 53, figs. 3-5 



This species recalls Callavia crosbyi Walcott.^ It differs in having 

 a more tapering glabella, smaller palpebral lobes, and in the absence 

 of a strong occipital spine. The cephalon of Callavia burri Walcott ^ 

 is very similar, but, as may be seen by comparing figures 9 and 10 of 

 the latter with figure 5, plate 53, of Callaz'ia perfecta, the palpebral 

 lobes are larger and farther out from glabella. 



Callavia perfecta has 17 thoracic segments and a very small, narrow 

 pygidium. The exterior surface has a very minute fretwork of lines 

 that is difficult to be seen even with a strong lens, in this respect 

 differing from the associated Callavia eucharis. 



Formation and locality. — Lower Cambrian : (6ik) Mahto forma- 

 tion ; dark, hard siliceous shale ; northeast base of Mumm Peak above 

 ]\Iural Glacier on west side of Hitka Pass, 6 miles (9.6 km.) in a 

 direct line north of summit of Robson Peak and northwest of Yellow- 

 head Pass, in western Alberta, Canada. 



' Smithsonian Misc. Coll., Vol. 53, No. 6, 1910, p. 284, pi. 28. 

 "Idem, pi. 28. figs. 9 and 10. 



