NO. 5 CAMBRIAN TRILOBITES RESSER 45 



STROTOCEPHALUS, n. gen. 



Diagnosis. — Cranidium alone available. Facial suture diverges an- 

 teriorly to rather sharp anterior angles ; glabella tapering with faint 

 furrows ; occipital furrow shallow ; occipital ring slightly thickened. 

 Brim wide, concave, and without a rim, striated vertically ; eye lines 

 developed ; palpebral lobes of moderate size, situated far back. 



Comparisons. — Differs from Alokistocare in two points, viz, sharper 

 anterior angles and more posterior position of the eyes. 



Genotype.- — ■5'. gordonensis, n. sp. 



Name. — ^TpoTo<i = spread, Ke<^aAos = head. 



Range. — At present confined to Middle Cambrian. 



Strotocephalus gordonensis, n. sp. 



Ptychoparia pylas Walcott (part), Smithsonian Misc. Coll., vol. 67, no. 2, 

 pi. 6, fig. 4c, 1917. (Other figs. Elrathia.) 



Middle Cambrian, Gordon; (Iocs. 4q, 4v) Gordon and Youngs 

 Creeks, Ovanda quadrangle, Montana. 

 Holotype. — U.S.N.M. no. 63743. 



WEEKSINA, n. gen. 



Two species from the Upper Cambrian of the House Range referred 

 to the Middle Cambrian genus Asaphiscus are distinct in many 

 respects. 



Diagnosis. — Entire trilobite ovate ; convexity not determinable. 

 Facial suture diverges anterior to the eyes arid is intramarginal two- 

 thirds of the distance to the center so that the anterior angles are 

 strongly rounded. Glabella wide, roimded in front ; glabellar fur- 

 rows short, but fairly deep. Brim of moderate width ; rim thickened 

 and, owing to course of the suture, sharply narrowed toward anterior 

 angles. Fixed cheeks narrow ; eyes fairly large ; palpebral lobes 

 strongly bowed. Free cheeks with well-defined rim and blunt genal 

 angles. 



Thorax with 10 or 12 segments ; tips of pleura blunt ; long spine on 

 axis of next to last or third from last pleuron. 



Pygidium half the size of the cephalon ; axis well defined, rather 

 wide, and extending nearly to rear margin ; axial and pleural furrows 

 distinct. 



Surface granulose. 



Genotype. — Asaphiscus ? imispinus Walcott. 



Range. — Presumably early Upper Cambrian. 



