UEECHINUS GIGAXTEUS. 



155 



mentary phyllodes include six to seven pairs of pores towards the ambitus 

 (Pis. 72, fig. l ; 73, fig. /). In a small specimen of U. Naresianus of 13 mm. 

 there are but two pairs of pores (PI. 74, fig. 6) representing the phyllodes. 



It is interesting to note that the actinal edge of the primordial inter- 

 ambulacral plates forms with its close tuberculation a rudimentary bour- 

 relet (PL 73. fig. /) separating the ambulacra! areas, a character greatly 

 developed in such genera as Conolampas, Conoclypus, Eehinolampas, and 

 the like. 



6 

 93 mm. 



Fig. 2i.'4. Ukechintfs giganteus. 



5 



80 mm. 



Fig. 225. U. giganteus. 



On the abactinal side of the test (PI. 74, fig. ,.') the pores are placed 

 towards the lower side of the ambulacral plates. 



In the abactinal system the anterior genital plates (PI. 74, figs. 1, j) 

 are united in a single plate which also carries the madreporic body, Figs. 

 224, 225. The odd anterior ocular plates abut against this composite 

 genital ; the anterior lateral ambulacra are separated by an elongated inter- 

 calated central plate which abuts on the anterior side against the abactinal 

 plates of the anterior lateral interambulacra, and on the other against 

 the posterior genitals, which with an intercalated plate separate the bivium 

 from the trivium. against which abuts the ocular of the right posterior ambu- 

 lacrum. There are no anterior lateral oculars. The ambulacral tube of the 

 odd anterior ambulacrum does not pierce the odd ocular plate (PI. 74, fig. 4). 



