DESCRIPTION OF GENERA AND SPECIES. 165 
Lisania ajax (Walcott). 
Plate 15, Figures 18, 18a. 
Arionellus ajax WALCOTT, 1905, Proc. U.S. Nat. Mus., vol. xxrx, 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: (C12) Gray limestone near the 
top of the middle limestone member of the Kiu-lung group [Blackwelder 1907a, 
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 (C40), 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 Li San. 
Lisania alala (Walcott). 
Plate 15, Figures 19, 19a—d. 
Arionellus alala WaLcotr, 1905, Proc. U.S. Nat. Mus., vol. xxrx, 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: (C51) Lower part of gray crys- 
talline limestone in the upper portion of the oolitic part of the Ch’ang-hia limestone 
[Blackwelder, 19074, p. 33 (part of the first list of fossils)], at Ch’au-mi-tién, Shan- 
tung, China. 
Collected by Eliot Blackwelder. 
A somewhat similar and possibly identical form occurs at about the same 
horizon (C4), limestone nodules at the base of the lower shale member of the Kiu- 
lung group [Blackwelder, 1907a, 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 (( 22), 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 (C30) 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 m.) on top of the 
long north and south ridge at Ch’ang-hia, Shan-tung; also (C46), light gray, crystal- 
