412 CENTROSTEPHANUS RODGEESII. 



secondaries, and suddenly increase rapidly in size, when they carry long 

 spines like all the rest of the coronal plates. 



Palermo ; Canary Islands. 



Centrostephanus Rodgersii 



!Thrichodiadema Rodgersii A. Ac, 18G3, Prop. Acad. X. S. Pliila.. p. 354. 

 ! Centrostephanus Rodgersii A. Ac, ]s72. Rev. Ech., Pt. 1, p. 98. 



PL III"./, is; PL XXIV. f. 87. 



The two primary rows of tubercles of the ambulacra! zone are closely 

 crowded together, owing to their size, which is nearly as large as the princi- 

 pal primary tubercles of the interanibulacral area. The median ambulacral 

 line is occupied by a zigzag vertical line of miliaries. The poriferous zone 

 is narrow; pores large, distinct. In the interanibulacral space there are two 

 principal vertical rows of tubercles larger than the others, flanked by two 

 shorter vertical rows towards poriferous zone, and one vertical row on each 

 side of the median line: all these tubercles are somewhat smaller than those 

 of the primary rows of the ambulacral zone, and considerably smaller than 

 those of the two principal interanibulacral rows. The miliaries are mod- 

 erately closely packed between the rows of smaller tubercles. The actinal 

 system is large, with but slight actinal cuts. Verticillations of spines close; 

 they are so arranged that spines appear irregularly longitudinally striated. 

 Outline of tesl circular from above, seen in profile regularly arched ; abac- 

 tinal part of test flattened, turban-shaped. Auricles slight, with a low con- 

 necting ridge and large auricular arch. Madreporic genital exceeding 

 greatly in size the other genital plates. Genital plates pentagonal, three 

 separated by a rectangular anal plate, the other two, adjoining madreporic 

 genital plate, by a smaller triangular plate ; genital opening large, placed 

 near outer edge, irregularly covered by small tubercles. Three of the 

 ocular plates are irregularly hexagonal, with outer rA^c rounded; the 

 three shortest sides forming the broadest outer edge of the plate; the other 

 two adjoining madreporic genital are triangular. Small elliptical plates cover 

 the whole anal system; a few only, somewhat larger, having a small tubercle, 

 carrying minute spines. Buccal membrane, in addition to the ten large 

 buccal plates, carrying small secondary spines, strengthened by longitudinal 

 plates, in continuation of ambulacral system. 



According to Dr. Stimpson, the color is deep reddish-purple when alive. 



Australia ; New Caledonia. 



