Vol. L Sun— Cambria n Faunas of North China (iv) 09 



1916 Ptychaspis Walcotti: Faunes Cambriennes de L'Extreiue-Orient Meridional, pp. 33-34, pi. V, 

 fig. 10 a-i, fig. 11 a-b. 



Dr. Mansuy Described this species very fully and the translation of the descrip- 

 tion is as follows: — 



' 'The two species attributed to the genus Ptychaspis Hall found in the Cambrian 

 of Upper Tonking, are very imperfectly known, being represented only by fragments of 

 heads, by a few free cheeks and thoracic segments, and by pygidia which seem to be 

 closely related to the forms of the same genus described by Mr. Walcott from the 

 Cambrian of Shantung and of Shansi, 



"The species herein described is represented by two varieties, well differentiated 

 in their propoi-tions, one with a longer glabella the other with a shorter glabella; the 

 glabella of the first is somewhat contracted. These differences in the length and width 

 of the glabella, sepai-ating these two forms, seem furthermore to repi*esent only individual 

 variations, for, as we will see later, very characteristic details of oiganization of specific 

 order are common to both. Ptychaspis angulata nov. sp., described further on, found in 

 another locality than Pt. walcotti nov. sp., is also represented by two vai-ieties differentiat- 

 ed in the same degree and possessing common specific characteristics as strong as those 

 observed in both varieties of the preceding species. In both Pt. walcotti and Pt. angulata 

 the two varieties differ in certain parts but are similar in their fixed common charac- 

 teristics. If we add that no intermediate variety has been observed, with one partial 

 exception, in spite of the large number of specimen gathered, we are forced to the deduc- 

 tion (with due reservations) that the two varieties of our species are perhaps but the 

 expression of sexual differences. 



"We will describe in the first place the long yai-'mty oi Pt.tvalcotti (nov. sp. ). 

 The glabella of the long variety of this species is subrectangular, the anterior side and the 

 posterior side measuring in a large individual 11 mm. and 15 mm. The convexity is 

 fairly well marked without reaching the high relief shown by certain species of the same 

 genus. The longitudinal incurvation becomes progressively accentuated from the middle 

 of the length and ends anteriorly in a rather abrupt curve. Dorsal furrows large and 

 very deep, their depth being increased by the increased height of the fixed cheeks. The 

 occipital furrow, equally well marked, deeper laterally and inflected backwards in the 

 same parts, is slightly sinuous in the middle. Anterior lobe rectangular, the anterior 

 edge of the glabella being almost straight, very gently convex. It is much wider than 

 long and limited backwards by transverse marginal furrows, not very noticeable. The 

 second lateral furrows, are still very oblique backwards, deeply furrowed, are separated 

 one from the other by an interval equal to their length. The third lateral furrows are 



