214 THE CHICAGO ACADEMY OF SCIENCES. 



posteriorly. At the inner margin of the limb, a narrow, deeply 

 impressed furrrow separates it from the median convex portion 

 of the head, laterally and anteriorly. The median portion rises 

 vertically or is even slightly overhanging from the bottom of 

 the bounding furrow to a height a little above the highest por- 

 tion of the limb, the direction of the surface then changes ab- 

 ruptly to a gently convex curve nearly to the central elevated, 

 axial portion or glabella which is surrounded by a slightly 

 flattened area.' The glabella is narrow and is abruptly elevated; 

 posteriorly it is produced laterally into a pair of flattened, 

 rounded lobes but little differentiated from the cheek surfaces. 

 Upon each cheek a little back from the anterior extremity of 

 the glabella and nearly half way between it and the furrow at 

 the margin of the limb, is a small conical point-like ocellus slightly 

 elevated above the general surface. 



Thorax and pygidium unknown. 



The dimensions of the type specimen are: width 19.5 mm., 

 total length of head to genal extremities, approximately 24 mm., 

 length of head along median line 12 mm., width of limb in front 

 5 mm., length of glabella 5.5 mm., width of glabella in front of 

 basal lateral lobes 3.3 mm., distance between ocelli 5.5 mm. 



Remarks. This species has not yet been observed within 

 the Chicago area, the type specimens being from Wisconsin. 

 It may, however, be looked for at Chicago. The species is the 

 first representative of the genus which has been recognized in 

 the Silurian faunas of America, although members of the genus 

 are not uncommon in the European faunas of similar age. 

 This American species more or less closely resembles several 

 European forms, but it is characterized by the deep furrow at 

 the inner margin of the limb. 



The species is named in honor of Mr. E. E. Teller, of Mil- 

 waukee, Wisconsin, in whose collection the type specimen is 

 preserved. 



Locality. Milwaukee, Wis. 



Order. II. OPISTHOPARIA Beecher. 



"Free cheeks generally separate, always bearing the genal 

 angles. Facial sutures extending forward from the posterior 

 part of the cephalon within the genal angles, and cutting the 

 anterior margin separately, of more rarely uniting in front 

 of the glabella. Compound paired holochroal eyes on free 

 cheeks, and well developed in all but the most primitive family." 

 Beecher, Zittel-Eastman Text Book of Paleontology, p. 266. 



