Vol. 1. Sun — Cambrian Faunas of North China (iv) 71 



whole surface of these lobes is covered by fine sinuous lines, drawn close together, 

 resembling cracks, interrupted or joining, whose general direction is parallel to the 

 edge. 



' 'The glabella of the second variety of Pt. walcotti, of almost equal length and 

 breadth, shows a subtrapezoidal contour; its longitudinal inflection becomes abruptly 

 accentuated towards the anterior third of its length. The length and obliqueness of the 

 anterior lateral furrows, the anterior concavity of the third lateral furrows, continuous, 

 reproduce all the traits of the corresponding parts of the long variety. The marginal 

 anterior rim is equally very wide, arched and contiguous to the glabella. This glabella 

 of the short form, seem to represent the glabella of the long form but shortened, as if 

 contracted with a stronger incurvation. 



"Similarities and differejstces. The 14 species of Upper Cambrian trilobites 

 from Shantung and from Shansi, attributed to the genus Ptychaspis Hall, by Mr, 

 Walcott, are all as poorly represented as are ours, by very mutilated heads, sometimes 

 reduced to internal moulds of dorsal teguments from the glabella and from the fixed 

 cheeks, by a few incomplete free cheeks and by three pygidia. From such insufficient 

 material we may only venture on some limited comparisons, all conclusion being 

 forbidden, particularly as we foresee that a revision of these forms based on the study 

 of less fragmentary specimens, will modify in a large measure the interpretation which 

 has heretofore been given, either by the reduction of the number of species already 

 described, or by the reference of some of them to other genera. 



"Among the Chinese species, Pt. walcotti (nov. sp. ) represents closer affinities 

 with Ptychaspis acamus Wale, from the Upper Cambrian limestone of the Chau-Mi-Tien, 

 in Shantung. The glabelK of Pt. acamus joins intermediate proportions to those of the 

 two varieties of Pt. walcotti; its anterior edge is more convex. The occipital ring is 

 smaller; finally in the Tonking species, the convexity of the long varirty, in its anterior 

 half, is much fainter, while it is more marked in the short variety. The granulations 

 which cover the surface of our species, are bigger and closer and through the superficial 

 structure of the integuments, Pt. walcotti draws closer to Pt. cadmus Wale, a species from 

 the same locality as Pt. acamus; besides, Pt. acamus, Pt. cadmus and Pt. campe Wale, 

 from Shantung, resemble each other closely. The differences in the proportions of the 

 glabella, in the height and in the relative development of the frontal lobe and the lateral 

 lobes, in these species, are faint, they vary in fact, very little from Pt. walcotti, and the 

 comparison of the figures given by Mr. Walcott with those representing Pt. walcotti in 

 the same work, will give a more exact notion of the similarity of these three Chinese 

 species between them, and with the Tonking species, than the best description. 



