CAMIiKlAX TRlLor.ITES — \\'AI,COTT 23 



Family OLKxtD.^v Salter 

 ORYCTOCARA, new genus 



Dorsal shield small, elliptical. Cephalon semicircular in outline, 

 from one-third to one-fourth the length of the dorsal shield ; genal 

 angles and free cheeks unknown ; cranidium subquadrangular in 

 outline exclusive of the narrow postero-lateral limbs ; glabella sub- 

 quadrangular in outline, with three lobes and an occipital ring; the 

 lobes are separated by very slightly defined, transverse furrows 

 terminating in round pits within the lateral margin of the glabella. 

 The facial sutures cut the posterior margin of the head within the 

 genal angles and pass inward and slightly forward to the base of 

 the eye and thence about the palpebral lobe and forward with a 

 slightly outward curvature to the frontal rim. Fixed cheeks broad. 

 Eyes long, with the margin of the palpebral lobe extending across 

 the fixed cheeks as an ocular ridge. 



Thorax with eleven segments ; pleurae with straight furrows and 

 abrupt, truncated ends. 



Pygidium large, with central axis divided into several rings by 

 transverse furrows, all of which extend across the pleural lobes to 

 the outer margin. 



Genotype. — Oryctocara gcikici, new species. 



Observations. — The cranidium of the cephalon of this genus is- 

 much like that of Orycioccphalns Walcott,^ but the thorax and 

 pygidium are unlike. The pleurfe are of the Olcmis Salter type in 

 having a straight median furrow, while the pygidium is broad and 

 of the Bathyitriscus- type. (See pi. i, fig. 2, of this paper.) 



The genus is referred to the order Opisthoparia Beecher and to 

 the famil}' Olenidse Salter. 



Only one species from the central portion of the Middle Cambrian 

 is now known. 



ORYCTOCARA GEIKIEI, new species 



Plate i. Figures 9, 10 



Dorsal shield small, longitudinally elliptical in outline, moderately 

 convex. Cephalon semicircular in outline, a little less than one- 

 third the length of the dorsal shield ; free cheeks and genal angles 

 unknown ; a narrow, rounded rim extends across the front of the 

 cranidium and it is probable that it continued along the free cheeks 

 and terminated in a small genal spine. Cranidium subquadrangular 



' Walcott, 1886, Bull. U. S. Geol. Survey, No. 30, p. 210. 



' Meek, 187.3, Sixth Ann. Rept. U. S. Geol. Survey Territories for 1872, p. 484. 



