NEW OSTRAOODERM— 0RVIG 



9 



pis, over the whole post-orbitopineal portion of the carapace (Eastman, 

 1917, p. 239, pi. 12, figs. 5, 6; Bryant, 1936, pp. 416-417, pi. 1; 0rvig, 

 in MS. , b) , and possibly continuing backwards on to the trunk behind 

 the carapace, and the pol3'gonal plates probably formed a fairly regu- 

 lar pattern in the interspaces between the crests and anteriorly to 



Figure 2. — Pycnaspis splendens, new genus, new species. Ornamentation of the 

 exoskeleton: a, shagreen of small tubercles belonging to an early stage of growth, in super- 

 ficial view (mainly after USNM 21334, X30); b, large tubercles belonging to a late stage 

 of growth, in oblique lateral view (USNM 21335, X30). 



them. On the other hand, there are no plates and scales in the 

 material similar to those which, in Astraspis, exhibit shallow lateral 

 line grooves on their external face (0rvig, in MS., b; see also Walcott, 

 1892, pi. 4, fig. 1). If not purely comcidental, this circumstance may 



