DESCRIPTION OF GENERA AND SPECIES. 139 



It differs from it in having a more elongate glabella, which is more transverse in 

 front. It is also not probable that species of this character would range through 

 2,500 feet (762 m.) of limestone. It is often the case that cephala that appear to 

 have the general features of Ptychoparia are found to belong to other genera when the 

 thorax and pygidium are known. This species is associated with Ptychaspis ceto, 

 Ill&nurus dictys, Menocephalus ? depressus, and Cyrtoceras cambria. 



Formation and Locality. Upper Cambrian: (C5G) Lower part of Ch'au-mi- 

 tien limestone, 25 feet (7.5 in.) below the top of Pagoda Hill [Blackwelder, 19070, p. 

 42 (part of last list of fossils)], i mile (1.6 km.) west of Tsi-nan, Shan-tung, China. 



Collected by Eliot Blackwelder and Li San. 



Conokephalina maia (Walcott). 

 Plate 13, Figure 13. 



Ptychoparia (?) maia WALCOTT, 1906, Proc. U. S. Nat. Mus., vol. xxx, p. 592. (Discussion of species 

 essentially as below.) 



This species is represented by one fairly good specimen of the central portions 

 of the cephalon, to which the description of Ptychoparia (Emmrichella) bromus [p. 135] 

 applies, with the exception that the latter has broader fixed cheeks and a flatter 

 frontal rim. Conokephalina maia also has short, strong palpebral ridges that are not 

 present in P. (E.) bromus. 



The type specimen of the cephalon has a length of 4.25 mm. 



Formation and Locality. Middle Cambrian: (C70) Oolitic limestone about 30 

 feet (9 m. ) above the base of the Ki-chou limestone [Willis and Blackwelder, 1907, p. 

 144 (last list of fossils)], 4 miles (6.4 km.) south-southwest of Tung-yii, Shan-si, China. 



Collected by Eliot Blackwelder. 



Conokephalina vesta (Walcott). 

 Plate 13, Figures 9, ga-c. 



Ptychoparia vesta WALCOTT, 1906, Proc. U.S. Nat. Mus., vol. xxx, p. 590. (Species described and 

 discussed essentially as below.) 



Of this species the central portions of the cephalon are known, also associated 

 free cheeks and pygidia. The parts of the cephalon preserved show it to have been 

 moderately convex, and semicircular in outline. Glabella convex, not very promi- 

 nent, broadly truncato-conical in outline ; antero-lateral angles rounded, front gently 

 curved ; between the base and front the sides are slightly incurved at a point about 

 two-thirds the distance from the base of the front ; three pairs of glabellar furrows 

 that extend about one-half the distance from the sides toward the center are faintly 

 impressed; occipital furrow narrow, shallow, and transverse; occipital ring narrow 

 at the sides, widening toward the center where the surface is on the plane of the 

 glabella ; dorsal furrow narrow and clearly defined at the sides, and shallow in front 

 of the glabella. 



Fixed cheeks a little more than one-half the width of the glabella, nearly flat 

 opposite the palpebral lobes, curving gently downward posteriorly to the posterior 

 furrow, and rather abruptly downward to merge into the frontal limb; palpebral 

 lobes a little less than one-half the length of the cephalon, narrow, and separated 

 from the fixed cheeks by rather strong, curved furrows ; palpebral ridge low, rather 

 strong, and extending obliquely forward from the anterior edge of the palpebral 

 lobe to the side of the glabella, just back of its antero-lateral angle; frontal limb 

 short, gently convex, and sloping down from the front of the glabella to the rounded 

 furrow formed by its merging with the frontal rim; frontal rim nearly flat and rising 

 at a low angle from the furrow. 



