DESCRIPTION OF GENERA AND SPECIES. 141 



associated pygidium has a proportionately shorter axial lobe and its sides curve 

 outward instead of inward. 



Formation and Locality. Middle Cambrian: (35r) Fu-chou series, limestones 

 near the base of the series just above the white quartzite [see Blackwelder, 19076, 

 p. 92, for general section giving stratigraphic relations], collected in a low bluff on 

 the shore of Tschang-hsing-tau Island, east of Niang-niang-kung, Liau-tung, 

 Manchuria, China. 



Collected by J. P. Iddings and Li San. 



Crepicephalus damia Walcott. 



Plate 13, Figures 14, i^a-h. 



Crepicephalus damia WALCOTT, 1905, Proc. U. S. Nat. Mus., vol. xxix, p. 92. (Described and discussed 

 as a new species essentially as below.) 



Cephalon semicircular in outline, with the postero-lateral angles terminating 

 in round, somewhat incurved spines. Glabella moderately convex, with the sides 

 narrowing slightly toward the front, which is broadly rounded; length a little 

 greater than its width at the occipital furrow; marked by three pairs of furrows; 

 the posterior pair extends obliquely inward and backward so as almost to separate 

 a triangularly shaped lobe; second pair rather faint, extending directly inward a 

 distance of about one-third the width of the glabella, and then curving slightly 

 backward; anterior pair very faint; occipital furrow rather broad and strongly 

 defined; occipital ring narrow at the ends, rounded, and rather strong in the central 

 portions; dorsal furrow clearly defined on the sides, but obscure in front of the 

 glabella. 



Fixed cheeks about one-half the width of the glabella; posteriorly they slope 

 downward into postero-lateral limbs that are about twice as long as the width of 

 the fixed cheeks; toward the front the fixed cheeks slope abruptly downward and 

 merge into the frontal limb ; palpebral ridges low and broad, merging into the strong 

 palpebral lobe ; postero-lateral limbs grooved near the posterior margin by a strong 

 furrow; frontal limb short, almost flat, and sloping abruptly from the front of 

 the glabella down to the strong, nearly flat, frontal rim; the body of the associated 

 free cheek is subquadrilateral in outline, marginal borders strong, clearly defined, 

 and produced behind a strong, slightly curved, rounded spine. 



Thorax unknown. 



The associated pygidium is quadrilateral in outline, exclusive of the strong, 

 slightly diverging postero-lateral spines, which are a little longer than the length 

 of the pygidium; sides of the pygidium subparallel or slightly diverging toward 

 the base of the spine; posterior margin nearly transverse; axial lobe prominent, 

 convex, and reaching nearly to the posterior margin; the sides converge slightly 

 toward the bluntly pointed posterior end; divided by three transverse furrows 

 into three segments and a strong terminal portion, which is marked at the point 

 where the axis slopes abruptly downward by a small node on each side ; the pleural 

 lobes are limited to a rather large anterior lobe, and an obscure secondary lobe, 

 which appears to merge backward into the postero-lateral spine. 



Surface apparently smooth under a strong lens; a few scattered punctae occur 

 on the glabella. 



The largest cephalon has a length of 10 mm., with a width of 12 mm. at the 

 palpebral lobes. 



This species differs from Crepicephalus iowensis Owen [1852, p. 573], to which 

 it appears to be most nearly related, by the form of the frontal limb and rim of the 

 glabella and other details; the pygidium is not so broad, and it also differs in outline. 



