44 PEOP. p. M. DTJNCAIf'S REVISION OP THE 



Test moderate to very large, tumid at the circular or slightly 

 polygonal ambitus, swollen, suhhemispherical or depressed abac- 

 tinally, flat actinally ; more or less flexible. The calcareous 

 deposits of the plates limited, the edges of the plates membranous. 



Apical system central, polygonal, projecting ; the plates sepa- 

 rated by membrane, and some anal plates intervening between 

 the basal and radial plates. Periproct small ; anus projecting. 



Ambulacra straight, broad at the ambitus; plates very numerous 

 and much bent vertically, overlapping from above actinally, and 

 overlapped by the ends of the interradial plates ; a pair of pores 

 in each plate, and two small plates in the adoral sutural membrane, 

 each with a pair of pores. Plates continued from the peristomial 

 edge to the mouth, imbricating, each plate broad, low, and pore- 

 pierced. Small primary perforate, non-crenulate, areolated 

 primary tubercles, in two or more vertical rows. 



Interradia with numerous broad, low, pistol-shaped plates, united 

 by membrane along the transverse edges, and expanded and over- 

 lapping at the median line; overlap in the opposite direction to 

 that of the ambulacra ; two or more vertical rows of primary 

 tubercles resembling those of the ambulacra. 



Peristome with small branchial incisions ; internal branchiae 

 very large and five in number, the external branchise small ; 

 lower tentacles with prehensile discs, the abactinal pointed and 

 branchial. Perignathic girdle weak, but with a decided arch 

 between continuous processes. 



Jaws with a small foramen ; teeth grooved. Spines delicate, hol- 

 low, fenestrated, longitudinally striated and ridged, variable in 

 length, but never very long ; the secondary spines small, sharp 

 and numerous, pointed, some sheathed. Pedicellarise numerous, 

 various, tridactyle, four-valved, some sharp and others blunt- 

 ended. 



Mecent. N. Atlantic to coast of Portugal, Florida, Caribbean 

 Sea, China Seas, Java, Philippines, Indian Archipelago, Ceylon, 

 Piji, New Zealand. From 100 to 450 fathoms. 



