NO. 5 UPPER CAMBRIAN TRILOBITES RESSER 95 



ELVINIA UTAHENSIS, new species 

 Plate i8, Figures 5, 6 



Except for the fact that this is such an important element of the 

 fauna, this pecuHarly weathered cranidium would have awaited the 

 finding of additional material before its description. Strangely enough, 

 this is the only Elvinia specimen found in large collections from the 

 locality. In spite of its poor preservation this cranidium allows the 

 specific characteristics to be ascertained. 



The glabella tapers forward at a normal rate to a truncate front. 

 Only a very shallow rear pair of furrows is visible, and the wide 

 (xxipital furrow is also shallow. The brim, occupying nearly a third 

 of the cranidial length, is separated into a thickened rim and a slightly 

 wider convex preglabellar area. Eyes normal in size and position, 

 and are not strongly bowed. The posterolateral limbs are long. 



St. Charles limestone; (loc. 546) Blacksmith Fork, Bear River 

 Range, Utah. 



Holotype.—'US.'HM. No. 108813. 



ELVINIA RUEDEMANNI, new species 



Plate 18, Figures 7-10 



Ruedemann identified this form as E. matheri. However, very 

 considerable differences in brim structure and the granulated surface 

 exist. It is not certain that the larger and smaller cranidia here 

 illustrated belong to the same species, for none of the smaller heads 

 is well preserved, although it is clear that they are granulated. E. 

 rucdcmanm belongs to a group which may eventually have to be 

 separated from Elvinia, but at present the altered appearance resulting 

 from depression of the preglabellar area does not seem to warrant 

 such action. 



E. riiedemamii is characterized by a rather rapidly tapering glabella. 

 Two pairs of furrows are developed, the anterior pair being short and 

 shallow while the deeper rear pair is connected as usual. The rather 

 large eyes are so far forward that their anterior ends are on a line 

 with the front margin of the glabella. At this point the fixigenes are 

 more than half the glabellar width. Rearward the fixigenes expand 

 less rapidly than the glabella, and extend into large posterolateral 

 limbs. The brim occupies about one-fourth the cranidial length and 

 consists of a thickened rim nearly circular in cross section. The rim 

 is less than half the width of the depressed preglabellar area. The 

 surface is covered with granules except on the preglabellar area where 

 vertical anastomosing lines take their place. 



