Helderberg Formation in Maeyland 51 



with tlie middle of tlic three lobes of the glabella, and a similar projecting 

 plate from the inner anterior angle of the cheek touches the front lobe of 

 the glabella near its anterior angle. Axis of the body convex, nearly as 

 wide as the lateral lobes ; pleura convex and straight for half their length, 

 and then gently curved downwards and llattened, grooved along the center. 

 Caudal shield with eight rings in the middle lobe ; lateral lobes with six 

 flat ribs strongly bent downwards ; surface granulate, with larger tubercles 

 on the glabella and other parts. 



" The specimens examined are all imperfect, and the surface markings 

 are also more or less obliterated. The characteristic features are the deep 

 furrow along the front and cheek margins, and between the glabella and 

 cheeks, and the projecting lobes from the inner margins of the cheeks which 

 touch or unite with the glabella, arching over the axial furrow. In the 

 two separated cephalic shields, the portion beyond the facial suture is 

 wanting, and in the more entire specimen it is too obscure to be char- 

 acterized." Hall, 1852. 



Occurrence. — Helderberg Formation, Keyser Member. Cash 

 Valley, Devil's Backbone, Maryland ; Keyser, West Virginia. 



Collection. — U. S. National Museum. 



Family PHACOPIDAE 



Genus DALMANITHS Emmrich 



Dalmanites aspinosus Weller 



Plate XCI, Fig. 16 



Dalmanites aspinosa Weller, 1903, Pal. N. J., vol. iii, p. 252, pi. xxii, fig. 15. 



Description. — " Known only from the pygidium which is longitudinally 

 semielliptical in outline, obtusely pointed posteriorly. Axis regularly 

 tapering and rounded posteriorly; in the type specimen reaching to within 

 4.5 mm. of the posterior margin, which makes it about six-sevenths of the 

 entire length of the pygidium; marked by about 16 annulations, which 

 gradually decrease in size posteriorly until they become entirely obsolete. 

 The pleura are rather strongly convex to the margin, with no flattened or 

 concave border; marked by ten prominent, narrow grooved ribs, which 



