298 FRED J. PACK 



Location: Himon Mine, Chisholm Mine, Abe Lincoln Mine, Half 

 Moon Mine, and at the upper water tank near Pioche. 



Ptychoparia Kempi, n. sp. 



(Plate III, Fig. i.) 



This form is known only by the head inside of the free cheeks. 



General outline of the head moderately quadrate; width, exclusive of postero- 

 lateral Hmbs, about equal to height. Glabella short, conical, with straight lateral 

 sides converging from base forward to gently rounded front ; slightly longer than 

 one-half height of head; one and one-half times longer than posterior width; 

 marked by three pairs of glabellar furrows, pointing directly across and nearly 

 uniting at center; moderately well-marked occipital groove, which deepens into 

 pit near lateral margin of glabella; occipital ring slightly convex, and provided 

 with well defined knob, or perhaps spine. 



Frontal limb broad, and concave toward front, where it turns slightly upward, 

 forming a narrow frontal rim; half as high as wide; marked with fine stria 

 radiating from front of glabella and extending about half-way to anterior rim; 

 antero-lateral portion broadly rounded. 



Fixed cheeks separated from glabella by deep dorsal furrows; elevated inside 

 eye-lobe, and forming a cone or rounded pyramid the apex of which is nearly 

 twice as high as glabella; anterior slope more gentle than posterior, which pitches 

 abruptly down into postero -lateral groove; fixed cheeks moderately broad, slightly 

 contracted just in front of eye, and then expanded into broad anterior limb. 



Eyes narrow, reaching from front of glabella to opposite elevation on fixed 

 cheek. 



Postero-lateral limbs elongate, narrow, curving gently backward, and traversed 

 part way out by groove. 



The species P. suhcoronata is a closely allied form, but P. kempi 

 may be readily distinguished from it by the absence of the peculiar 

 boss in front of the glabella, and by the presence of the elevations on 

 the fixed cheeks. 



The one specimen by which this form is known preserves only the 

 glabella, frontal margin, free cheeks, and postero-lateral limbs. It is 

 fairly well preserved, and is contained in a brown shale tinted with 

 green. 



Location : Half Moon Mine. 



GENUS ZACANTHOIDES, Walcott 



Zacanthoides, Walcott, 1888: American Journal of Science, Third Series, Vol 

 XXXVI, p. 165. 



