6 



PANAMIC DEEP SEA ECHINI. 



and the left anterior alone are connected ; the three others are separated 

 by the next series of anal plates, — large plates of the second series which 

 have reached the genital ring, Fig. 18. In a female of 28 mm. there are 



28 in in ,f 

 Fill IS. Pokocidaris Mtli.eki. 



2S mm. V . 



Fig I' 1 Poroi idaris Mii.i eri. 



again three of the primitive anal plates connected, the anterior and the 

 two left lateral plates (PI. 7, fig. ..'), as in the youngest specimen of 14 mm. ; 

 but the right lateral plates arc not in contact. They arc separated by large 

 anal plates of the second series, and tlie posterior plates arc separated by 

 two secondary anal plates, Fig. ID. But in spite of the irregularity of posi- 

 tion of the five plates of the second series, it is easy to recognize them, 

 as well as those of the third and fourth series, in all the stages we have 

 described. 



In Porocidaris Cobosi the plates of the second series seem to force their 

 way to the genital ring in a more regular manner, as is easily seen in com- 



8 mm. 



Fir;. 20. Porocidaris Cobosi. 



35 mm. 



Fio. 21. Porocidakis Cobosi. 



paring the anal plates of a young P. Cobosi of 8 mm., Fig. 20 (PI. 12, fig. /). 

 with those of one of 35 mm., Fig. 21 (PI. 11, fig. 6). With the exception 



