DESCRIPTION OF GENERA AND SPECIES. 165 



Lisania ajax (Walcott). 



Plate 15, Figures 18, 180. 



A rionellus ajax WALCOTT, 1905, Proc. U.S. Nat. Mus., vol. xxix, p. 58. (Species described essentially 

 as below.) 



Cephalon, exclusive of free cheeks, subrhomboidal in outline, convex. Glabella 

 moderately and uniformly convex, sides converging very slightly from the base to 

 the rounded front ; slight traces of short furrows are shown by reflected light ; occip- 

 ital furrow a faint, transverse depression that separates the glabella from a fairly 

 strong, slightly convex occipital ring; dorsal furrow narrow but clearly defined. 



Fixed cheeks very narrow and sloping away from the glabella toward the palpe- 

 bral lobes; posteriorly they slope forward into a rather large postero-lateral limb; 

 anteriorly they slope rapidly to the frontal limb; palpebral lobes prominent, about 

 one-fourth the length of the cephalon ; frontal limb gently convex, rounded in front, 

 and without traces of a frontal rim. 



Surface smooth under a strong lens. 



The type specimen of the cephalon has a length of 4 mm. 



In form the cephalon of this species is somewhat like that of Lisania alala 

 (Walcott). It differs in the absence of an occipital spine and in being proportion- 

 ately somewhat narrower. 



Formation and Locality. Middle Cambrian: (012) Gray limestone near the 

 top of the middle limestone member of the Kiu-lung group [Blackwelder 19070, 

 pp. 37 and 41 (part of the first list), and fig. 10 (bed 7), p. 38], 3.25 miles (5.2 km.) 

 southwest of Yen-chuang, and (040), limestone nodules in green shales in the middle 

 limestone member of the Kiu-lung group [idem (part of the first list of fossils)], in a 

 gully in bank of river 2 miles (3.2 km.) south of Yen-chuang, Sin-t'ai district, Shan- 

 tung, China. 



Collected by Eliot Blackwelder and L,i San. 



Lisania alala (Walcott). 

 Plate 15, Figures 19, iga-d. 



Arwr.ellus alala WALCOTT, 1905, Proc. U. S. Nat. Mus., vol. xxix, p. 59. (Species characterized as 

 below.) 



In general form and proportion the central parts of the cephalon of this species 

 are much like Lisania agonius [p. 164]- They differ in the proportionately smaller 

 elongate glabella, nearly flat frontal limb, and a thin instead of a rounded margin. 



Formation and Locality. Middle Cambrian: (051) Lower part of gray crys- 

 talline limestone in the upper portion of the oolitic part of the Ch'ang-hia limestone 

 [Blackwelder, 19070, p. 33 (part of the first list of fossils)], at Ch'au-mi-tien, Shan- 

 tung, China. 



Collected by Eliot Blackwelder. 



A somewhat similar and possibly identical form occurs at about the same 

 horizon (04), limestone nodules at the base of the lower shale member of the Kiu- 

 lung group [Blackwelder, 19070, pp. 37 and 40 (second list of fossils), and fig. 10 

 (bed 4), p. 38], 3 miles (4.8 km.) southwest of Yen-chuang, Sin-t'ai district, Shan- 

 tung; also (022), Ch'ang-hia limestone in upper oolitic portion [idem, pp. 22 and 33 

 (part of last list of fossils)], at Ch'ang-hia, Shan-tung, and (080) layer in black 

 oolite of the Ch'ang-hia limestone [idem, 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 in.) on top of the 

 long north and south ridge at Ch'ang-hia, Shan-tung; also (04(5), light gray, crystal- 



