DERMAT0D1ADEMA GLOBULOSUM. 



61 



Tn a specimen 30 mm. in diameter the ten buccal plates are connected 

 for their whole length and cover a relatively greater part of the actinal 

 system (PI. 26, fig. .'), more as we find them in young specimens of D. 

 horridum (PI. 25, figs. 7, 2); the plates are rounded at the proximal 

 extremity, the ambulacra! pore is protected distally by a prominent lip, the 

 distal part of the buccal plates is covered with miliaries and secondary 

 tubercles. The narrow belt left between the outer faces of the buccal 

 plates and the edge of the actinal system is filled with small narrow elon- 

 gate actinal plates irregularly arranged. 



In a specimen of 25 mm. (PI. 28, lig. 3) the ocular plates are flat penta- 

 gons, with rounded corners, leaving large cuts between them and the adjoin- 



25 mm. 



Fig. 90. Debmatodiadema globttlosdm. 



30 mm. (fragment). 



Fii.. 91. Debmatodiadema olobulosum. 



ing rectangular genital plates. The ambulacral base of the ocular plates is 

 longer than the base of the genitals, which project slightly further than the 

 oculars into the anal system. The genitals and oculars are covered with 

 miliaries. The oculars carry in addition one or two secondary tubercles 

 on the anal edge. 



In a specimen of 30 mm. in diameter the proportions between the 

 oculars and genitals are somewhat different. The oculars have nearly 

 twice the base of the genitals, and three of them (PI. 28, fig. 4), the odd 

 and the right and left anterior oculars, have split into two plates which 

 appear like plates intercalated between the genitals and oculars, reach- 

 ing in one case the anal system. These plates look much as if inter- 

 ambulacral plates had forced their way to the anal system and were to 

 separate, as in some Spatangoids, the bivium and the trivium. In this 

 older specimen the anal edges of all the apical plates carry an outer line 

 of secondaries. 



