82 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 148 



three-fourths the length of glabella plus occipital ring. Border furrow 

 showing in most specimens a slight median inbend. Palpebral area 

 half of the glabellar width, slightly upsloping ; ocular ridge transverse. 

 Palpebral lobe 0.4 times the length of glabella plus occipital ring; 

 distance to posterior cranidial margin slightly greater than length of 

 palpebral lobe. Anterior facial sutures slightly more divergent than 

 the average in the genus ; anterior angles of cranidium more widely 

 rounded than in most species. Posterior area as wide (tr.) as occipital 

 ring. Free cheek with wide border well defined anteriorly, the border 

 furrow fading out posteriorly ; genal spine convex on upper face, 

 rather long, somewhat curving inward. 



Pygidium somewhat more than twice as wide as long. Axis occupy- 

 ing somewhat less than a third of the width, tapered, showing at least 

 on internal impression 3 rings plus a terminal section, extended into 

 a broad, low postaxial ridge. Anterior outline of pleural lobes and 

 furrows curving backward, producing well-rounded anterior angles. 

 Doublure fairly wide laterally, reduced medially. Posterior margin 

 rather straight in median portion, with suggestion of a slight median 

 notch. 



Surface of cranidium and free cheeks punctate in the furrows, 

 especially in the anterior border furrow where the puncta are larger. 

 Length of largest (holotype) cranidium 20 mm. Length of pygidium 

 2.6 mm., width 5.5 mm. 



Discussion. — The cranidium is somewhat similar to A. laxa in the 

 longitudinal profile of the frontal area, differing from that species in 

 the proportionately longer (sag.) border, more widely rounded anter- 

 ior angles, longer palpebral lobe, lesser distance from palpebral lobe 

 to posterior margin, narrower (tr.) posterior area, and punctate sur- 

 face. The pygidium is unlike A. laxa and much more like A. tarda in 

 the lesser relative width and rounded sides. The rather strong diver- 

 gence of the anterior facial sutures and median inbend of the border 

 furrow give the cranidia of this species some resemblance to Aphelaspi- 

 della macropyge, but the pygidium is definitely of the Aphelaspis type. 



Occurrence. — The type locality is U.S.G.S. 2970, Monroe County, 

 where it occurs in association with Aphelaspidella macropyge, Aphe- 

 laspis arses, and Paraphelaspis vigilans. These species indicate the 

 lower portion of the middle Aphelaspis zone. A few, imperfect cranidia 

 in the collection cnqV4 from the Lost Creek section may belong to 

 this species, but, especially in the absence of the pygidia, cannot be 

 distinguished with certainty from A. laxa. The stratigraphic position 

 would confirm the assignment indicated above. 



Ty/'^.y.— Holotype : U.S.N.M. 144646. Paratypes: U.S.N.M. 

 144647. 



