NO. 7 PTYCHOPARIID TRILOBITES — RASETTI 23 



about one-third the glabellar length, situated at the level of the glabel- 

 lar midpoint. Width of pali>ebral area somewhat over half the 

 glabellar width. Posterior limbs as wide (tr.) as the occipital ring, 

 with a deep furrow reaching the extremity. Anterior facial sutures 

 slightly divergent for some distance in front of the eyes, curving 

 inward after crossing the marginal furrow ; frontal portion slightly 

 ventral. Posterior branch first directed straight outward, then curving 

 backward to posterior margin. 



Type species. — Austinvillia virginica Resser. 



Remarks. — The cranidium of Austinvillia resembles Onchocephalus 

 in the general proportions and convexity but differs in the structure 

 of the frontal area and the slight divergence of the facial sutures. 

 The structure of the frontal area and the lesser convexity of the 

 various parts also distinguish Austinvillia from Antagmus, Eoptycho- 

 paria, and Piasella. 



The type species is the only described form that can be assigned 

 to the genus. However, a closely similar species is common in leached 

 dolomite at the base of the Parker shale three-fourths of a mile south- 

 west of Parker Cobble, near Georgia, Vt. 



AUSTINVILLIA VIRGINICA Resser 



Plate I, figure 5; plate 4, figures 8-10 



Austinvillia virginica Resser, Geol. Soc. Amer. Spec. Pap. 15, p. 61, pi. 3, figs. 

 8-10, 1938. 



Available material. — The type lot includes the holotype and two 

 paratypes preserved in limestone. An additional, perfect cranidium 

 was collected by the writer. 



Description. — Only details not mentioned in the generic diagnosis 

 are included. The glabella shows four pairs of short furrows of in- 

 creasing strength. The furrows of the first, third, and fourth pairs 

 start from the dorsal furrow, while the second pair is located some- 

 what more inward. This feature is common to a great number of 

 both ptychopariid and corynexochid Cambrian trilobites, and its sig- 

 nificance is obscure. The occipital ring bears a node. Palpebral lobes 

 slightly exceeding one-third the glabellar length ; distance from pos- 

 terior end of palpebral lobe to posterior margin equal to length of 

 palpebral lobe. Surface finely and rather indistinctly granulated. 

 Length of largest cranidium 14 mm. 



Remarks. — The cranidium from Quebec here figured differs slightly 

 from the holotype and paratype illustrated by Resser in the lesser 

 convexity of the border, while it seems identical with a third, un- 



