Plate 12. 

 1-12. Porocidaris Cobosi A. Ag. ; Station 3404. 



1. Abactinal system of specimen measuring 8 mm. in diameter, 



2. Actinal system of the same specimen as fig. 1. 



3. Part of actinal system of specimen measuring 10 mm. in diameter. 



4. Showing resorption of odd and right anterior interambulacral plates adjoining actinos- 



torae, same specimen as fig. 1. 



5. Right anterior ambulacral plate showing pore and secondary tubercle of same speci- 



men as fig. 1. 



6. Showing resorption of right and left posterior ambulacral and odd posterior interambu- 



lacral plates adjoining the actinostome in specimen measuring 21 mm. in diameter. 



7. Showing the same in a specimen measuring 35 mm. in diameter. 



8. Abactinal extremity of the left posterior ambulacrum, seen from the interior, showing 



the broad gap left between the ocular and the interambulacral plates, held togetli'T 

 by thin calcareous threads. 



9-11. Papillfc covering the genital openings of specimens measuring 10 mm. (figs. 9, 11) 



and 21 nun. in diameter (fig. 10). 

 12. l*rimary spine of specimen measuring 35 mm. 



