ECHINODERMA TA—ECHINOIDEA. 



593 



long, open at the ends; ambulacral grooves on under side single 

 or bifurcating twice; periproct between peristome and border. 

 Eocenic-Oligocenic. 



33. M. quinquefaria Say. Oligocenic. 

 Slightly wider posteriorly, but in general subcircular; periproct 



approximately at two fifths of the distance from margin to peri- 

 stome. 

 Vicksburgian of Georgia and Cedar Keys, Florida. 



34. M. rogersi Conrad. Oligocenic. 

 Subpentahedral, with peristome more strongly depressed than in 



preceding; ambulacral petals wider, open in front; periproct 

 nearer to margin than in preceding. (Type of genus.) 

 Vicksburgian of Georgia and Mississippi. 



XXII. Mellita Klein. 

 Test flat as in Scutella, but with five or six usually closed lunules, 

 or more rarely open cuts, one at the end of each ambulacrum, and 



'^C''<-^^w^/ 



Fig. 1926. Mellita caroliniana, ventral, lateral and dorsal views, slightly 

 reduced. (After McCrady.) 



one in center of posterior interambulacrum ; posterior petals long- 

 est; periproct at proximal end of posterior lunule, close to the 

 mouth. Pliocenic-Recent. 



35. M. caroliniana McCrady. (Fig. 1926.) Pliocenic. 



Slightly wider behind; posterior lunule twice as long as others. 



Differs from the recent M. sexforis Lamarck of the Atlantic coast 



38 



