Plate 4. 

 1-12. Dorocidaris panamensis A. Ag. 



1. Youngest left anterior interambulacral plate of specimen 30 mm. in diameter, showing 



the first trace of a primary tubercle ; Station 3368. 



2. 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. 



3. A genital plate with its opening protected on one side by long digitate tubercles ; 



Station 3397. 



4. Tart of madreporic plate of specimen measuring 25 mm. in diameter. 



5. Sixth posterior interambulacral plate from the actinostome of same specimen as fig. 4. 



G. Genifal plate witli numerous pores, of specimen measuring 14 mm. in diameter ; 

 Station 3397. 



7. Part of scrobicular area of primary tubercle, on sixth plate from the actinostome, 



left anterior interambulacral area of same specimen as fig. 1. 



8. rriiuary loft anterior interambulacral tubercle, on the fifth plate from the actinostome 



of suiiie specimen as fig. 1. 



0. R;i(li()l»! of primary inti'rambulacral area of same specimen as fig. 1. 



10. rriniary interambulacral radiole of specimen measuring 20 mm. in diameter; 



Station '.VA[)7. 



11. I'riinary interambulacral radiole of same specimen as fig. 10, with serrations modified 



into granules. 



12. Slightly magnified granular structure of a primary interambulacral radiole of a speci- 



nu'ii UM-asuring 25 niiu. in dianu'tcr; Station 3397. 



