Vol 1. Sun — Cambrian Faunas of North China (iv) 67 



Ptychaspis angulata Mansuy vai. chinensis Sun 



Plate V, Figs. 1 a, b. 



1915 Ptychaspis angulata Mansuy. Faunes Cambriennes du Haut-Tonkin, p. 26 pi. Ill, fig. 2 a-v. 

 Mem. Serv- Geol. de I'lndochine. Vol. IV, fasc. II. 



1916 Ptychaspis angulata Mansuy. Faunes Cambriennes de L'Extreme-Orient Meriditional, pi. V, fig. 12 

 a-e. Pi. VI, fig. 1 a-d. 



Mansuy described this species very fully, the translation of his description being 

 as follows : 



"The glabella is subrectangular, a little larger at the base than at the anterior 

 extremity. The anterior lobe is roundly arched ; the dorsal furrows, deep and narrow, 

 are faintly sinuous. The first lateral furrows, well marked, very obhque behind, spread 

 over two-thirds of the width of the glabella; they seem really to represent a second pair, 

 the first pair of lateral furrows being frequently erased in species of this genus. The 

 following furrows (transverse furrows) very deep, parallel to the preceding lateral ones, 

 are continuous. Occipital furrow sinuous. The lower edge of the head, the occipital 

 furrow, the lateral furrows and the anterior edge of the glabella are about equidistant in 

 both varieties. In the middle of the occipital ring, a striking tubercle is noticeable in 

 most samples; this tubercle, often broken at the top, gave rise to a spine more or less 

 developed. 



"Fixed cheeks very narrow, with a variable convexity, usually fairly well 

 marked. Ocular lobes about semicircular, sinuous anteriorly, are contiguous to the gla- 

 bella and join it in a very short ocular line. Frontal limb narrow, almost fiat with a 

 large arched tubercle in the middle; its width equal to that of the marginal rim, which is 

 larger in the middle than laterally, and is separated from the limb by a large but not deep 

 furrow. The anterior edge of the head is not curved but forms a very open obtuse angle. 

 The sutures, very oblique in their posterior portion up to the ocular lobes, are sinuous; 

 after having passed these occular lobes they become rectilinear and parallel to the axis of 

 ' the glabella before reaching the anterior margin. The free cheeks though dissociated, 

 are easily dififerentiable one from the other according to width. The surface is regular- 

 ly convex, with the maximum convexity at the center. The marginal rim, large and 

 elevated, with curved section, enlarges more and more until it reaches the genal angle. 

 The posterior rim of the cheeks is much narrower. The genal spine, long, strong, acicular, 

 with circular section, ia nevertheless at its base much smaller than the peripheric rim. 

 The lower edge of the free cheeks forms a concave arc with large radius near the genal 

 angle. 



"The dissociated thoracic segments show that the rachis was salient, with curved 

 section. The pleurae are large and are traversed by a well-marked, slightly oblique 

 furrow; the pleural ends are inflected backwards. Some of the pygidia are arched, others 



