24 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 128 



figured specimen in the type lot. Hence the small differences may be 

 attributed to intraspecific variability. 



Occurrence. — The types are from U.S.N.M. locality 23J : Shady 

 ( ?) limestone, i mile northeast of Austinville, Va. The specimen 

 here figured is from boulder G-25, Grosses Roches. 



Types. — Holotype and paratypes : U.S.N.M. No. 94742. Plesio- 

 type: U.S.N.M. No. 123878. 



Genus PERIOMMA Resser, 1937 



Description. — Glabella conical, more or less truncated in front, 

 faintly furrowed at the sides, high posteriorly, not greatly elevated 

 anteriorly. Dorsal furrow very deep laterally. Occipital furrow well 

 impressed, occipital ring rounded. Frontal area consisting of pre- 

 glabellar field, often with median boss, and strongly convex, swollen 

 border. Palpebral area slightly convex, on the average upsloping; 

 ocular ridges distinct ; palpebral lobes shghtly raised, about one-fourth 

 the glabellar length, at the level of the glabellar midpoint. Width of 

 palpebral area about three- fourths width of glabella. Posterior limbs 

 about as wide (tr.) as, or slightly wider than, occipital ring; distal por- 

 tion narrower (tr.) than proximal portion. Posterior marginal fur- 

 row deep, but not extending to the end of the limb, indicating that it 

 does not continue onto the free cheek. Anterior facial sutures slightly 

 convergent ; frontal portion slightly ventral. Posterior branch first 

 directed outward, gradually curving backward to posterior margin. 

 Test thick ; upper surface may be finely granulated. 



Type species. — Periomma typicalis Resser. 



Remarks. — The characters of the genus, based on the poorly repre- 

 sented type species, have been supplemented from two other species, 

 P. walcotti Resser and P. gaspensis described herein, both appearing 

 to be definitely congeneric with P. typicalis. The genus is fairly well 

 characterized by the elevation of the palpebral area, which chiefly 

 distinguishes it from more generalized ptychopariids. However, 

 transitional forms seem to link Periomma to Onchocephalus. 



PERIOMMA WALCOTTI Resser 



Plate I, figure 6; plate 5, figures 9-14 



Periomma walcotti Resser, Geol. Soc. Amer. Spec. Pap. 15, p. 92, pi. 3, figs. 

 14, IS, 1938. 



Available material. — The type lot includes the holotype and a para- 

 type. The U.S.N.M. collections include several other topotype 



