288 RESEARCH IN CHINA. 



length 14 mm., width 22.5 mm., width of axis anteriorly 6.8 mm., length of axis 9.5 

 mm., width of concave marginal border about 4 mm. The most marked differences 

 between the two species are the much more conspicuous concave border in A. chi- 

 ncnsis, and the slight though obscure traces of segmentation upon both the axis and 

 the pleural slopes. This latter character, however, may be due to the removal of 

 the test from the central portion of the specimen, and if the external surface were 

 preserved it might be as smooth as A. Icevis. 



Asaphus sp. undt. (plate 26, fig. 9). 



A small pygidium may be referred provisionally to the genus Asaphus and it 

 may be an immature individual of one of the larger forms already described. It is 

 semicircular in outline, with a slightly concave, sloping marginal border. The axis 

 is rather sharply defined but not greatly elevated, and is divided into eight or nine 

 indistinct segments. The pleural slopes are smooth. The dimensions of the speci- 

 men are: length 3.5 mm., width 5.5 mm. 



Asaphus sp. undt. (plate 26, fig. 14). 



A nearly complete hypostome may be referred to this genus, and it possibly 

 belongs to one of the associated species that have been described from the pygidia. 

 The specimen has a moderately deep emargination in front and has the central por- 

 tion strongly differentiated from the lateral expansions, these characters serving to 

 distinguish it from a much larger Isotelns-like hypostome with which it is associated. 

 The dimensions of the specimen are: length 7.5 mm., width 6 mm., depth of emar- 

 gination 2 mm. 



Asaphus ? sp. undt. 



In addition to the asaphids already noted, several other species are represented 

 in the collections, all of them in a fragmentary condition, some of which are clearly 

 distinct from any of those described. Two incomplete free cheeks and an eye occur 

 which may or may not belong to some of the forms described from pygidia or cranidia, 

 also two or three incomplete pygidia and an incomplete cranidium. 



Isotelus ? sp. undt. (plate 26, fig. 13). 



A very imperfect specimen of a small Isotehts-like pygidium is included in the 

 collection. It is a mere fragment, yet so far as it is preserved it is not unlike a 

 small example of the North American species /. gigas. 



Isotelus sp. undt. (plate 26, fig. 15). 



An incomplete specimen of a large forked hypostome is evidently from a species 

 of this genus. The extreme width of the specimen is about 34 mm., the depth of the 

 emargination 18 mm., and its width externally 25 mm. This hypostome closely 

 resembles that of the North American species /. gigas, but it is too incomplete for 

 certain specific identification. 



Megalaspis minor Weller (plate 26, fig. 8). 



1907. Megalaspis minor Weller, Proc. U. S. Nat. Mus., vol. xxxn, p. 563. 



Pygidium small, subelliptical in outline. Axis scarcely elevated above the 

 general surface, about one-third of the total width of the pygidium anteriorly, taper- 

 ing to the rather bluntly rounded posterior extremity, divided by nearly obsolete 

 depressions into eight or nine obscure segments. Pleural slopes regularly convex 

 from the sides of the axis to the margins, without a differentiated marginal border, 



