ECHINODERMATA—CYSTOIDEA. 



463 



upper surface of each arm but on one side. Column round and 

 smooth. Ordovicic. 



7. A. florealis Billings. (Fig. 1769.) Ordovicic. 

 Each calyx plate with low ridges radiating from a centrally 



placed tubercle to the angles. Arm much longer upon posterior 

 side than upon anterior. Calyx about one and one half inches 

 long. (Type of genus.) 

 Trenton of Ontario. 



VI. Glyptocystites Billings. 

 Calyx elongate cylindrical, with four series of plates ; four plates 

 in the basal and five in each succeeding series. Anal opening in 

 one of the plates of the second series. Mouth at center of summit 

 where it receives the five ambulacra. Ambulacra bordered with 

 small plates. Pectinate rhombs 10 to 15. Column short, tapering 

 to a point. Ordovicic. 



8. G. farbesi Billings. Ordovicic. 

 Surface of plates with four to six large ridges which radiate 



from the center of the plate to the center of each straight side of 

 the plate. In the angular spaces formed by these large ridges 

 are smaller parallel ones. The entire surface of each plate is also 

 covered with sharp concentric striae. Length about two inches; 

 diameter three fourths inch. 

 Chazy of Quebec. 



9. G. multiporus Billings. (Fig. 1770.) Ordovicic. 

 Four of the ambulacra extending to base of calyx, the fifth but 



Fig. 1770. Glyptocystites multiporus, anterior and dorsal views of two specimens; 

 a, analysis of calyx, showing pore-rhombs and place for arms. (After Billings, Can, 

 Org. Rem. Dec, ill.) 



