44 PKIMORDIAL PERIOD. 



pleiu'ae bhintly ^jointed at tlieir outer ends, the points not being directed 

 very strongly backward ; their inner ends so joined to the axial segments 

 that they have the appearance of lapping a little upon them just inside the 

 dorsal furrow; grooved, the groove being deepest about midlength, where 

 the outer and inner portions of its front border meet at a distinct but very 

 obtuse angle ; grooves extending from the dorsal fuiTOw nearly to the 

 extremity of the plem^se, Avhere they disappear. 



Pygidiiim somewhat semicircular in outline, distinctly trilobate ; seg- 

 mentation indistinct, so much so in some of the specimens that the surface 

 appears nearly as plain as that of an Asaphus, but the segmentation is 

 usually more distinctly shown upon surfaces from which the cnist has been 

 removed; axis prominent, especially at its distal end, Where it terminates 

 abiiiptly at the inner edge of the broad marginal border; segments of axial 

 lobe eight or ten ; lateral lobes much depressed, a little wider than the axial 

 lobe at the anterior end, and narrowing to an incTirved point at the end of 

 the axis ; the whole exterior margin having a broad, flat border of nearly 

 uniform width tlnoughout ; the under surface of this border marked by 

 fine, somewhat in-egular, longitudinal ■ strias, such as are usu.ally seen upon 

 corresponding parts of Asaphus. 



The largest specimen in the collections is about seven centimeters long. 



These specimens are the same that were used by Mr. Meek in his 

 description of this species, and upon which he also based his genus 

 Asa2}hiscus. 



Position and locality. — Strata of the Primordial period, probably of the 

 Potsdam epoch, near Antelope Spring, House range, Utah. 



Family PAKADOXID^. 



Genus OLENELLUS Hall, 1861. 

 Olenellus Gilbert! Meek. 



Plato II, lig. 3 o, h, c, d, and e. 



Olenellus Gilherti Meek, 1874 (manuscript). 



Olenellus Gilberti White, 1874, Geog. & Geol. Exp. & Surv. -west 100th Merid., Prelim, 

 liep. Invert. Foss., 7. 



Head subsemicircular or semi-oval, the length being to the breadth at 

 the posterior border about as four or five to seven; both the external and 



