DESCRIPTION OF GENERA AND SPECIES. 137 



Fixed cheeks a little wider than the glabella and nearly flat from the dorsal 

 furrow to the palpebral lobes; palpebral lobes large, situated opposite the central 

 portion of the glabella; palpebral ridges obscure, low and broad, and very clearly 

 defining the lateral portions of the fixed cheeks from the frontal limbs; frontal 

 limb narrow in front of the glabella, sloping downward to the broad, shallow furrow 

 that merges into the broad, almost flat frontal rim; postero-lateral limbs short; a 

 narrow, sharp furrow extends along their posterior margin from the glabella to the 

 facial suture, just within the posterior lateral margin. 



Surface minutely granular under a very strong lens. 



The largest cephalon has a length of 5 mm. 



This species is distinguished by the broad, flat fixed cheeks, convex, smooth 

 glabella, large palpebral lobes, and nearly flat frontal margin. 



Formation and Locality. Middle Cambrian: (C2?>) Upper part of thin-bedded 

 gray oolitic limestone at the base of the Ch'ang-hia formation [Blackwelder, 1907^, 

 p. 32 (second list of fossils), and fig. 6 (bed 20), p. 25], 50 feet (15 in.) below the base 

 of the cliffs i mile (1.6 km.) east-southeast of Ch'ang-hia, Shan-tung, China. 



Collected by Eliot Blackwelder. 



Genus LIOSTRACUS Angelin. 



Liostracus ANGELIN, 1854 (edition 1878), Pal. Scandinavica, pt. i, p. 27. (Described as a new genus.) 



Genotype. Liostracus aculeatus Angelin. 



The cephalon of Liostracus aculeatus has a smooth, convex glabella, a narrow, 

 flat, or slightly convex frontal limb, with a nearly flat or slightly convex margin that 

 in L. aculeatus is turned upward in relation to the plane of the margin of the ceph- 

 alon. I find some variation in this respect among a half dozen specimens from 

 Borgholm and Andrarum in the collections of the United States National Museum. 

 All of the specimens have small eyes, well-marked palpebral lobes and ridges, and a 

 strong occipital spine. Surface with many fine pits that give the impression that the 

 test may be porous, but of this there is not any proof, as the pits may be only a sur- 

 face character. I am inclined to the view that much of the so-called porous surface 

 is formed by the pits between the fine, low ridges that form a network on the outer 

 surface of the test. 



As far as known to me, no specimens of the entire dorsal shield of L. aculeatus 

 have been found. 



Among the species from China there do not appear to be any that come within 

 the restricted limits of Liostracus. Ptychoparia (Emmrichella) mantoensis [plate 13, 

 fig. i] and P. (E.) constricta [plate 13, fig. 5] approach most nearly, but they differ in 

 having a convex, instead of concave, frontal limb and in the absence of an occipital 

 spine. For convenience of comparison I have illustrated a specimen of the cran- 

 idium of Liostracus aculeatus Angelin from Borgholm [plate 13, figs. 6, 6a-b]. 



Genus CONOKEPHALINA Brogger. 



Conokephalina BROGGER, 1886, Geol. Foren. i Stockholm Forhandl., No. 101, vol. viu, pt. 3, p. 206. 

 (Names subgenus to include Conocephalites ornatus Brogger, 1877, Dikelocephalus osceola Hall, 

 but does not define subgenus.) 



Conocephalina Brogger, GRONWALL, 1902, Danmarks Geol. Unders., Raekke 2, No. 13, p. 150. (Uses 

 generic name, but does not define genus.) 



Conocephalina Brogger, LORENZ, 1906, Zeitschr. deutsch. geol. Gesellsch., vol. I.YIII, pt. n, p. 64. 

 (Revives genus Conocephalites, places Conokephalina Brogger in it, and takes a new type for Cono- 

 kephalina, in Conocephalites emmrichi Barrande.) 



Genotype. Conocephalites ornatus Brogger, 1877, Nyt Mag. Naturvidenska- 

 berne, vol. xxiv, p. 37, plate 3, figure 5. 



