210 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 64 



Burnet quadrangle, U. S. Geolog-ical Survey, shows that the head 

 waters of Clear Creek drain an area on its western side where the 

 Cap Mountain formation occurs, and it is from this area that the 

 type specimen undoubtedly came. In the collections made by Dr. 

 Cooper Curtice for the United States Geological Survey there are 

 specimens of a similar form collected in the Clear Creek drainage 

 area from Potatotop Hill, the upper portion of which is formed of 

 the Cap Mountain formation ; there are also specimens of the 

 cranidium from a locality in the Cap Mountain formation lo miles 

 northwest of Potatotop that are identical with those from Potatotop. 



Dr. Shumard's description of the cranidium and pygidium from 

 Clear Creek corresponds so closely to the specimens from Potatotop 

 that I do not hesitate to adopt the latter as the representative of the 

 species, although Shumard described the flattened frontal border 

 variety of the species, and the specimens from Potatotop have the 

 rounded and intermediate or semi-flattened border ; other specimens 

 from 10 miles northwest, near the Colorado River, show the narrow 

 rounded, intermediate and broad frontal border. 



The cranidium has a low, broadly conical glabella marked by 

 three pairs of short lateral furrows ; fixed cheeks narrow, moderately 

 elevated; frontal limb slightly convex, arching downward to a 

 strong, rounded transverse furrow (parallel to the front margin) 

 that has three elongate oval transverse pits, one of which is directly 

 in front of the glabella and one on each side in line with the posterior 

 lateral angle of the glabella ; frontal border gently convex, nearly 

 horizontal, and varying in width so as to be a little wider or narrower 

 than the frontal limb ; it varies in width, and may be convex or 

 almost flat. 



The palpebral lobes are not preserved, but Dr. Shumard in his 

 description stated that " a line drawn transversely across the middle 

 of the glabella, if extended, would pass nearly through to the center 

 of the eyes." This corresponds to the specimens from both Texas 

 and Alabama. 



The associated pygidium is described as follows : " Pygidium 

 short and somewhat massive, sub-elliptical, axis approaching semi- 

 cylindrical, elevated above the lateral lobes, as wide as one lateral 

 lobe, and occupying about two-thirds the length of the pygidium ; 

 rings four, separated by deep furrows ; posterior margin gently 

 arched in the middle and armed on either side with a long, curved, 

 diverging spine (about eight lines long) ; lateral lobes gently convex, 

 segments indistinct." ^ 



^ American Jour. Sci., 2d ser.. Vol. 32, 1861, p. 219. 



