222 RESEARCH IN CHINA. 



Surface of specimens preserved in the limestone nearly smooth or marked by 

 very minute shallow pits. 



Dimensions. A dorsal shield 30 mm. in length has the following dimensions: 



Cephalon: mm. 



Length . . . n.o 



Length of eye-lobe 3.5 



Width at posterior margin . 20.0 



Width of glabella at posterior margin 6.0 



Thorax : 



Length 12.0 



Width at fourth segment 19.0 



Width of axial lobe at first segment 5.5 



Width of axial lobe at ninth segment 4.0 



Pygidium: 



Length 7.0 



Width at union with thorax 12.0 



Fragments of this species are quite abundant in the limestones and interbedded 

 shales. A few entire specimens are found in a fine argillaceous shale a short distance 

 above the white quartzite at the base of the section, and it is from the best speci- 

 mens of these that the above description was drawn, together with specimens of 

 the cranidium in the limestone. 



In general outline and appearance Asaphiscus iddingsi approaches the type of 

 the genus, .4. wheeleri Meek [Walcott, 1886, plate 31, fig. 3]. Asaphiscus iddingsi 

 has a genal spine, a longer eye-lobe, a proportionately shorter cephalon, and nine, 

 instead of eight, segments in the thorax. 



Formation and Locality. Middle Cambrian : (35 r and 3(5 e) Fu-chou series, shales 

 interbedded with limestones near the base of the series just above the white quartz- 

 ite [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, L/iau-tung, Manchuria, China. 



Collected by J. P. Iddings and Li San. 



Genus ILL^NURUS Hall. 



Illaenurus canens Walcott. 



Plate 23. Figures 3, sa-c. 



Illtrnurus canens WALCOTT, 1905, Proc. U. S. Nat. Mus., vol. xxix, p. 96. (Described as a new species 

 essentially as below.) 



Cephalon, exclusive of the free cheeks, subrhomboidal in outline, moderately 

 convex. Glabella subquadrate, moderately convex, length and width the same, 

 without perceptible occipital or dorsal furrows; palpebral lobes small, with their 

 anterior end opposite the center of the glabella; frontal margin broadly rounded; 

 postero-lateral limbs short and subtriangular in outline; the facial suture, cutting 

 the frontal rim on a line with the base of the palpebral lobe, passes directly to the 

 anterior margin of the palpebral lobe; it encircles the latter, and then, curving 

 gently outward, passes in an almost direct line to the postero-lateral margin of the 

 postero-lateral limb. 



Surface minutely punctate under a strong lens. 



The pygidia associated with the cephalon parts are rounded subtriangular in 

 outline, and about two-thirds as long as the width of the anterior margin, rather 

 convex, and marked on the interior of the cast by a faintly defined, rather narrow 

 axis, and very slight traces of ten or more transverse furrows on the axis, that are 

 more faintly indicated for a short distance on the pleural lobes. 



The largest cephalon in the collection has a length of 14 mm., with the same 

 width at the palpebral lobes; a pygidium 14 mm. in length has a width of 20 mm. 



