23 



(PI. I. Fig. 1, 21) is large (21 mm. in the specimen of 90 mm. in diameter, on 

 which the description of the test is based), of the usual diadematoid structure, 

 all the ocular plates being contiguous with the periproct in their whole width; the 

 genital plates are not much elongated. Inside the ocular and genital plates there 

 is a band of small, irregular plates, carrying small spines; the median part of the 

 periproct is naked; there is (according to de Meijere) some variation in the 

 relative size of the naked median part of the periproct and the outer ring of plates. 

 There is a large analtube; a small papilla covers each genital opening. (In Astropyga 

 I have not been able to find such a papilla). A few small tubercles are found on 

 the genital plates. 



The interambulacral areas do not differ in any essential character from 

 those of Astropyga, as regards the abactinal side. The uppermost one in the outer 

 series of large tubercles is found on the 9th or 10th plate from above. It is said in the 

 preliminary description that „there is no distinct series of secondary tubercles on 

 either side of this series, only irregularly placed miliary tubercles". This is not 

 quite correct; there may be a rather distinct series of small tubercles on the almost 

 naked upper interambulacral plates. This series can be traced down to where 

 the large tubercles begin, and here a small tubercle at the upper and inner side of 

 the scrobicular area may be seen to succeed those of the upper plates. There 

 may thus be said to be an inner, longitudinal series of small tubercles along the 

 outer series of large tubercles. The inner series of large interambulacral tubercles 

 commence gradually on the following plates, the second series on the 10th or 11th 

 plate, the third series on the 11th or 12th plate etc. There are 12 longitudinal series 

 of large tubercles in all, arranged (on the actinal side) parallel to the median line 

 of the area, as in Astropyga puhnnata. On the abactinal side, however, the series 

 of tubercles are parallel to the outer edge of the area. The naked space with the 

 blue spots, parallel to the outer series of tubercles, disappears suddenlj' at the 

 ambitus, where a new series of tubercles occupies its place, as in A. puluinata; in 

 one of the specimens, however, the naked space disappears gradually at the ambitus 

 between the two outer series of large tubercles, as in A. radiata and as is also the 

 case in de Meijere's specimen. In this specimen the direction of the inner series 

 of large tubercles is a little more convergent towards the median line of the area 

 than is otherwise the case. The large median interambulacral space is set with 

 scattered miliary tubercles. 



The ambulacral areas in the large specimens are not raised above the 

 interambulacral areas; in small specimens I find them a little raised, as has been 

 stated by de Meijere. There is a primary tubercle on every compound plate, 

 whereas in Astropyga, — viz. in A. radiata and puluinata, — a primary tubercle is 

 found only on every second or third plate. These tubercles are smaller than the 

 interambulacral ones; the uppermost one is found on about the 10th plate fiom 

 above. Inside the primary tubercles some small secondary and miliary tubercles 



