162 PEOF. p. M. Duncan's eetision of the 



Marginal contour variable, eubcircular, snbpentagonal, narrow 

 and long or the reverse, usually truncated posteriorly. Five or 

 six lunules, usually closed, narrow and long, one in the median 

 line of the posterior interradium, the others in the ambulacra, 

 rarely developed as cuts. 



Apical system variable in position, central or excentric in 

 front, large, the madreporite central, the radial plates on its 

 flanks, the four genital pores in the interradia. 



Ambulacra petaloid abactinally, the posterior pair the longest, 

 all nearly closed, with broad poriferous zones, pores distant ; 

 interporiferous areas tumid, plates very low. Actinally the plates 

 are grooved simply and perforated near the peristome, the grooves 

 bifurcate more than once towards the edge of the test. A 

 single half-hidden spheridium in each groove near the peristome. 



Interradia very narrow abactinally, the apically placed plates 

 enclosing a genital pore in four areas ; discontinuous actinally 

 except in the posterior interradium. 



Peristome small, central or excentric in front, with an orna- 

 mented margin ; single interradial perignathic processes, short, 

 curved, bent backwards. Jaws above the processes, rather flat ; 

 teeth superior. Periproct small, at the proximal end of the 

 interradial lunule. 



Simple pillars and close radiating partitions connect the upper 

 and lower surfaces of the test near the edge inside, and extend 

 inwards as solid partitions and separate the ambulacral and intes- 

 tinal areas, and a cellular structure limits the jaws more or less. 

 Spines club-shaped abactinally, spathiform near the edges of the 

 lunules, actinally straight and long, and cylindrical and curved 

 near the ambulacral furrows. Actinal tubercles rather large, 

 with a raised warty intervening structure, abactinal tubercles 

 smallest. 



Fossil. Pliocene and Post-Pliocene : N. America. 



Mecent. Gulf of California, Panama to Peru, Gralapagos, West 

 Indies, N. and S. Carolina, Florida, Bermuda, Brazil ; (Red Sea?). 



Subgenus Mellitella. 



All the ambulacral lunules as open slits in the margin. Genital 

 pores four in number. Peristome and apical sjstem excentric 

 posteriorly. 



Recent. Guayaquil, Panama, Galapagos. 



To receive Mellita Stoiesi, Agass., sp. 



