Puate 4, 
1-12. Dorocidaris panamensis A. Ag. 
Youngest left anterior interambulacral plate of specimen 30 mm. in diameter, showing 
the first trace of a primary tubercle; Station 3368. 
Youngest posterior interambulacral plate more advanced than fig. 1; two lower second- 
ary tubercles are developed, the primary and two upper tubercles in process of 
formation. 
A genital plate with its opening protected on one side by long digitate tubercles ; 
Station 3397. 
Part of madreporic plate of specimen measuring 25 mm. in diameter. 
Sixth posterior interambulacral plate from the actinostome of same specimen as fig. 4. 
Genital plate with numerous pores, of specimen measuring 14 mm, in diameter ; 
Station 3397. 
Part of scrobicular area of primary tubercle, on sixth plate from the actinostome, 
left anterior interambulacral area of same specimen as fig. 1. 
Primary left anterior interambulacral tubercle, on the fifth plate from the actinostome 
of same specimen as fig. 1. 
Radiole of primary interambulacral area of same specimen as fig. 1. 
Primary interambulacral rasiole of specimen measuring 20 mm, in diameter ; 
Station 3397. 
Primary interambulaeral radiole of same specimen as fig. 10, with serrations modified 
into granules. 
Slightly magnified granular structure of a primary interambulacral radiole of a speci- 
men measuring 25 mm. in diameter; Station 3397. 
