188 ROYAL SOCIETY OF CANADA 



have a spinous or strongly tuberculated axis to the pygidium, and in this 

 respect appear to differ from the others.' 



Three species of this genus have been found in the conglomerate- 

 limestone bands of the gray shale at Hastings Cove. 



DoRYPYGE Wasatchensis, Hall & Whitfield, sp. 



Dikellocephalus Wahsatchensis, H. & W. Geol. Expl., 40th par., vol. iv., p. 241, 

 pi. i., fig. 35. 



Dikellocephalus gothicus, H. & W., lb. p. 242, pi. i., fig. 36. 



Olenoides Wahsatchensis, Walcott, U. S. Geol. Surv. Bull., 30, p. 189, pi. xxix, 

 figs. 2, 2a. 



var. AcADiCA, n. var. (PL IV., tig. 1.) 



We have remains of two pygidea which appear not to dilfer much 

 from this species. The original description of the pygidium on which 

 (J), gothicus) was founded is as follows : 



" Pygidium semiovate or short paraboloid, with a very strong cen- 

 tral axis and spinose margin, anterior margin straightened for about two- 

 thirds of the width of the lateral lobes, where it curves abruptly back- 

 ward to the lateral angles. Axial lobe strong, cylindrical and prominent, 

 forming one-third of the entire width, exclusive of the spines, and reach- 

 ing almost to the posterior margin of the shield ; obtusely rounded at the 

 extremity, and marked by six annulations exclusive of the terminal ones. 

 Lateral lobes very moderately convex, and marked by four divided ribs 

 on each side, each terminating in a strong and proportionately long 

 marginal spine ; central area of each rib depressed, forming a flattened 

 groove, extending to the base of the marginal spine. Border of the ribs 

 elevated, the anterior one strongest and prominent, gradually widening 

 from its origin to the margin of the shield ; posterior border narrow and 

 rounded, separated from the next succeeding rib by a sharply depressed, 

 narrow groove. This peculiar form of rib gives to the shield an appear- 

 ance similar to the grooving of a gothic arch. Margin of the shield 

 surrounded by twelve long, rather strong spines, four of which on each 

 side are about equal in size and strength, Avhile the four occupying the 

 posterior border are shorter and unequal, those in the middle being 

 shortest. 



"The peculiar feature in the specimen consists in the divided ribs of 

 the lateral lobes, and the spinous margin." 



In the Acadian form the rachis of the pygidium is narrower, but 

 unfortunately, being broken away its surface is unknown. The ribs on 

 the side lobes of the pygidium have the double groove described by 



1 Walcott's figures do not show this for D. Marcoui, but Whitfield's original 

 ones do. 



