DESCRIPTION OF GENERA AND SPECIES. 287 



Asaphus sp. cf. A. expansus Dalman (plate 26, figs.3, 4). 



This species is represented in the collection by two specimens, both of them 

 pygidia and both of them more or less incomplete. The dimensions of the two indi- 

 viduals are: length 12 mm. and 7.25 mm., width 19 mm. and 15.5 mm. The width 

 of the axis anteriorly is 7 mm. and 3.5 mm. The axis is bordered by rather broadly 

 rounded, impressed axial furrows, and its posterior extremity is about 2 mm. from 

 the posterior margin. The segmentation of the axis is obscure, but about seven or 

 eight annulations can be detected, the more posterior ones being almost obsolete; 

 upon the pleural slopes two or three obscure segments can be detected anteriorly. 



These pygidia are too imperfect to be identified with certainty as .-1 . expansus, 

 but if they do not belong to that species they certainly represent a closely allied form. 

 They are quite different from any of the North American Asaphidae, in fact no mem- 

 ber of the genus Asaphus in its strict sense is present in any of the American faunas. 



Asaphus asiaticus Weller (plate 26, tig. 5). 



1907. Asaphus asiaticus Weller, Proc. U. S. Nat. Mus., vol. xxxn, p. 561. 



Pygidium subsemielliptical in outline, moderately convex, the axis depressed, 

 bordered by rather broadly rounded axial furrows which become obsolete poste- 

 riorly ; pleural slopes prominent just outside the axial furrows, then sloping with a 

 convex surface to the margins, without a differentiated marginal border. Axis 

 occupying about one-third the total width of the pygidium anteriorly, tapering pos- 

 teriorly to a bluntly rounded point, divided by rather broad and shallow, obscure 

 furrows into twelve segments. Pleural slopes divided into about twelve obscure 

 segments which reach less than half-way from the axial furrows to the margins ; the 

 most anterior furrow crossing the pleural slope is broad and deep, being much more 

 conspicuous than those behind. 



The dimensions of the type specimen, an incomplete pygidium, are : length 20.5 

 mm., width about 30 mm., width of axis anteriorly 10 mm., length of axis 16 mm. 



This species is known only from the pygidium which is much like that of the 

 European A. expansus, being distinguished chiefly by its greater proportional length 

 and by the more obscure segmentation of the pygidium. 



Asaphus Isevis Weller (plate 26, fig. 6). 



1907. Asaphus Icei'is Weller, Proc. U. S. Nat. Mus., vol. xxxn, p. 562. 



Pygidium nearly semicircular in outline. The axis depressed, without segmen- 

 tation, poorly defined by the nearly obsolete axial furrows, occupying about one- 

 fourth of the total width of the pygidium anteriorly; pleural slopes smooth, without 

 segmentation, convex toward the axis but becoming depressed in a broad, moder- 

 ately concave marginal border toward the outer margin. The posterior extremity 

 of the axis reaches the inner margin of the concave border. 



The dimensions of the type specimen are: length 12 mm., width 23 mm., width 

 of axis anteriorly 5.5 mm., length of axis 8.5 mm., width of concave marginal border 

 about 3.5 mm. 



This species is represented in the collection by a single nearly complete pygid- 

 ium. vSo far as can be determined it seems to be a member of the genus Asaphus 

 in its strict sense, the species being especially characterized by its remarkably smooth 

 surface. 



Asaphus chinensis Weller (plate 26, fig. 7). 



1907. Asaphus chinensis Weller. Proc. V. S. Nat. Mus.. vol. xxxn. p. 56^. 



This species is founded upon a single, nearly perfect pygidium and is much like 

 the last-described form. It differs in its proportions, however, its dimensions being : 



