CEETROCIDARIS DOEDERLEINI. 



33 



Centrocidaris Doederleini A. Ag. 



Goniocidaris Doederleini A. Ag., Bull. M. ( '. Z. 1898. XXXII, No. 5, p. 73. Plate III, fig. 1. 



Plates 5; 14. figs. 1,2. 



Only a single specimen of this interesting species was collected. It is 

 allied to G. canaliculata, but can at once be distinguished from it by the 

 flatness of the test and the very slender primary radioles; they are cylin- 

 drical, finely striated, slightly tapering at the distal extremity, where they 

 are slightly fluted (PI. 14, figs. /, ,.'). The ambulacral secondary spines are 

 elongated, sharp, slender, slightly fluted ; those of the interambulacral areas 

 are longer and broader. When denuded, the bare interambulacral area is 

 seen to be shallow (Pis. 5, figs. 7, /, ; 14, iigs. 1, .'). The scrobicular area 

 of the primary tubercles is surrounded by a prominent row of secondary 

 tubercles, with a few secondary tubercles and miliaries irregularly scat- 



26 mm. showing ratio of test to aotinal syst. 



Centrocidaris Doederleini. Fig. 47. 



tered outside of it. The primary ambulacral tubercles run in two vertical, 

 slightly undulating lines, with two inner rows of miliaries between the outer 

 row and the bare median line (PI. 5, figs. 1-3) extending along the equatorial 

 zone of the ambulacrum, and single rows at the actinal and abactinal 

 extremities of the ambulacral areas (PI. 5, figs. 1-8). 



The first six pairs of ambulacral plates (after the upper pair) carry two 

 tubercles, Fig. 46, and subsequently three, one in each case being a second- 

 ary tubercle, the others miliaries (PI. 5, fig. .'). 



The poriferous zone is characterized by its great width (PI. 5, fig. 3) ; it 

 is as broad as the median ambulacral space between the vertical rows of 

 primary ambulacral tubercles, and by the depth of grooves connecting the 

 ambulacral pores. In the specimen figured, 26 mm. in diameter, there 

 were eleven plates in each ambulacral series of the actinal system and four 



