GENERA AND GBOUPS OP THE ECHINOIDEA. 157 



interporiferous areas with very numerous transverse rows of 

 pores for minute tentacles ; actinally and at the peristome is 

 a short groove, straight and perforate ; buccal pores large. A 

 single spheridium, covered, in each ambulacrum. 



Interradia narrow ; abactinally the highest plate is single, and 

 actinally the plates are continuous, and the peristomial plate is 

 single. 



Peristome small, central, polygonal, formed by ten ambulacral 

 and five interradial plates. Jaws well developed, with the teetli 

 superior and more or less inclined. Perignathie processes single ; 

 interradial, short, bent, placed beyond the limits of the pyramids. 



Periproct small, inframarginal. 



Pillars and partitions only in concentric parallel series near 

 the edge, within tlie test. Tubercles and surrounding miliaries 

 scattered, similar, usually largest actinally. Spines short, dorsally 

 cylindrical, slightly swollen, larger, longer, and cylindrical acti- 

 nally, many around the peristome and periproct. Large slender 

 tridactyle pedicellariae near the petaloid parts of the ambulacra ; 

 others with expanded tops on projecting stalks very general. 



Fossil. Tertiary: Europe, Asia, Java, N. Africa (Egypt), N. 

 America. 



Recent. East Indian Islands, Philippines, Pacific Islands, 

 Japan, Persian Gulf, Eed Sea, Mauritius, Zanzibar, Australia, 

 Tasmania, New Zealand. 



Eatnily Sctjtellid^, Agassiz, 18il, Monogr. d^Ech, viv. et foss. 

 livr. 2, p. 1. A. Agassiz, 1872-74, Revision, p. 524. 



Test very flat, margin incised or not, lunules or slits in the arese 

 or not. ximbulacral furrows bifurcating and branching. Peri- 

 stome flush. Jaws flat, teeth superior. Radiating partitions 

 between the floors internally. 



Genus Scutella. 



Subg;enus Echinarachnius. 

 Genus Echinodiscus. 

 Encope. 

 Subgenus Monophora. 

 Genus Mellita. 



Subgenus Mellitella. 



Astriclypeus, 

 Genus Lenita. 



Mortonia. 

 Rotul . 



