14 TROPICAL PACIFIC ECHINI. 



above the ambitus ; they are highly asymmetric, fan-shaped, and polygonal 

 (PI. 40, figs. 12~lJi) ; somewhat more abactinally from the ambitus the polyg- 

 onal radioles are smaller (PI. 40, figs. 15-17) ; midway between the ambitus and 

 the abactinal system the primary radioles of the odd ambulacrum are slightly 

 smaller than those nearer the ambitus (compare PI. 40, figs. 18-20, to PI. 40, 

 figs. 21-23) ; nearer the abactinal system the radioles have become still 

 smaller (PL 40, figs. 2Jt, 25; and PI. 40, figs. 26, 27). PI. 40, fig. 28, is 

 one of the miliary spines from the upper extremity of the right posterior 

 interambulacrum, hidden by the larger primary radioles. Figures of 

 some of the primary radioles of the anal system are given on PI. 40, figs. 

 29-32. 



Seen from the interior, there is a small triangular plate_between the actinal 

 plates of the odd posterior interambulacrurc/(Pl. 43, fig.£^and of the right (oi t^j 

 anterior interambulacruiYj which may be the remnant of the primordial plates 

 of these interambulacra. 



PoDOpnoRA Agass. 



Podophora atrata Agass. 



Pis. 2, figs. 1-3; 3% figs. 5-8; 16, figs.9-i.i; 17-28; 31, figs. 5-5. 



A fine specimen of Podopliora atrata, measuring 97 mm. including the 

 spines, is figured on PI. 21''. It was collected, with others, by the Hon. 

 Nicolas Pike, at Mauritius. When seen from above, it is of a dark violet, 

 almost black ; seen from the actinal side the marginal spines are of a light 

 violet color towards the tip, passing to a very light shade of the same color. 

 The smaller flattened and elongated actinal spines, as well as the miliary spines 

 of the buccal plates, are of the latter shade ; the actinal membrane is chocolate 

 bi'own. The larger marginal spines are of a somewhat lighter color on the 

 upper side, with a tinge of green ; the upper surface is also coarsely and 

 irregularly granular and pitted. On the lower side they are smooth or only 

 slightly pitted near the tip. 



A very interesting specimen of Podophora atrata from Mauritius is figured 

 on Plate 21", figs. 1-3. It is marked for the abnormal development of a number 

 of the ambital radioles. Instead of being merely cylindrical as is the case in 

 the large majority of the specimens examined they are club-shaped and pro- 

 portionally larger than the ambital radioles usually are. Their shape reminds 

 one somewhat of the club-shaped spines of Ciduris Bliimcnhachii 



