DESCRIPTION OF GENERA AND SPECIES. 177 



marked by two pairs of very slight, short furrows. The fixed cheeks are about 

 two-thirds the width of the glabella and moderately convex; palpebral lobes small, 

 and placed about their own length from the frontal rim; frontal rim apparently 

 very narrow, and separated from the glabella and fixed cheeks by a narrow, distinct 

 groove. 



Surface finely pustulose under a strong lens. 



Formation and Locality. Middle Cambrian: (CIO) Lower shale member of 

 the Kiu-lung group [Blackwelder, 19070, pp. 37 and 40 (part of the third list of 

 fossils), and fig. Sa (bed 35), p. 29], about 3 miles (4.8 km.) southwest of Yen-chuang, 

 Sin-t'ai district, Shan-tung, China. 



Collected by Eliot Blackwelder. 



A portion of a pygidium is also doubtfully referred to this genus from Locality 

 ('30, Middle Cambrian: layer in black oolite of the Ch'ang-hia limestone [Black- 

 welder, 19070, p. 33 (part of first list of fossils)], 25 feet (7.5 m.) above the second 

 cliff at an elevation of 1,700 feet (568.9 m.) on top of the long north and south ridge 

 at Ch'ang-hia, Shan-tung, China. 



Collected by Eliot Blackwelder. 



Genus LEVISIA Walcott. 



Lci'isia WALCOTT, 1911, Smithsonian Misc. Coll., vol. 57, No. 4, p. 86. (Described and discussed as 

 a new genus essentially as below.) 



This genus is proposed to include a group of small trilobites represented by 

 Agranlos agenor Walcott [19056, p. 44]. The cranidium is strongly convex; glabella 

 truncato-conical, tumid, and with only a trace of glabellar furrows; occipital ring 

 narrow at the sides, broadening rapidly toward the center, convex, and extending 

 backward into an obtuse spine. Frontal limb very narrow and passing almost 

 without any line of demarcation into the rather broad, slightly convex frontal margin 

 of the cephalon. Fixed cheeks tumid, about half as wide as the glabella, and with 

 small palpebral lobes midway of their length. Postero-lateral limbs rather short 

 and marked by a deep, narrow, intermarginal posterior furrow that separates a 

 narrow, rounded margin. 



Genotype. Agraulos agenor Walcott [19056, p. 44, and 1911, plate 15, fig. 7]. 

 A second species, Levisia adrastia (Walcott) [19056, p. 61], has the same generic 

 characters. Its surface has the same pitting and in addition a few relatively large, 

 scattered granules. 



Levisia adrastia (Walcott). 

 Plate 16, Figures 5, 50. 



Menocephalus adrastia WALCOTT, 1905, Proc. U. S. Nat. Mus., vol. xxix, p. 61. (Species described 

 essentially as below.) 



This is a minute cephalon, having a strongly convex, almost globular glabella 

 that rises abruptly from the deep dorsal furrow. A shallow furrow outlines small 

 postero-lateral lobes at the base of the glabella; occipital furrow narrow and distinct; 

 occipital ring slightly convex back of the occipital furrow, narrow at the sides, and 

 widening gradually toward the center. 



Fixed cheeks about one-half the width of the glabella, strongly convex; frontal 

 limb obsolete ; frontal rim about half as wide as the fixed cheeks, slightly convex, and 

 separated from the fixed cheeks by a transverse, narrow, shallow groove. 



Surface with shallow pits under a strong lens, with a few scattered larger 

 granules. 



