466 



NORTH AMERICAN INDEX FOSSILS. 



14. P. filitextus Billings. Ordovicic. 



Longer axes of rhombs in same direction as length of calyx. 

 Plates on flat side ten times larger than in P. squamosus. Plates 

 on convex side with strong ridges radiating from the center to 

 the angles ; between these are often other ridges crossing the 



P'iG. 1774. Pleurocystites squamostis, 

 two specimens showing opposite sides. O, Fig. 1775. Lepocrinites gebhardi, show- 

 anal opening. (After Billings, Can. Org. ing a pectinated rhomb and ambulacra. 

 Rem. Dec, III.) (After Hall.) 



sides of the plates at right angles, giving the plates a striated 

 appearance. Calyx about the size and shape of P. squamosus. 

 Trenton of Ottawa. 



15. P. elegans Billings. Ordovicic. 



Differs from P. filitextus in its smaller size, shorter rhombs, 

 and much stronger surface striation. Size of calyx about one half 

 that of P. filitextus. 



Trenton of Ottawa. 



IX. Lepocrinites Conrad. {Lepadocrinus Hall.) 

 Calyx oval or pear-shaped, composed of 20 plates arranged in 

 circular rows of four cycles. First or basal cycle consisting of 



