212 HAWAIIAN AND OTHER PACIFIC ECHINI. 



upper margin of the vertically truncate posterior end of the test. The sub- 

 anal plastron is oblique, flat or slightly convex, about 24 mm. wide and 14 mm. 

 high; five ambulacral plates, with four big tube-feet, enter into its composition 

 on each side. This is the arrangement in the smallest individual also but in 

 the specimen figured, there are only four ambulacral plates with three big 

 tube-feet on each side. It is to be regretted that owing to an indelible stain, 

 the composition of the subanal plastron does not show in the photographs 

 (PI. 160, figs. .2 and 3). The subanal fasciole is very distinct and the anal 

 branches arising from it, one on each side, run up nearly level with the top of the 

 periproct. The peristome is large and very little depressed. It measures 

 11 mm. in width by 6.5 mm. in length and is closely covered by some thirty 

 plates (more or fewer) of which an outer (anterior) series of eight covers more 

 than half the peristome; these eight are much larger than the rest and the 

 middle pair are fully 2 mm. square. The labrum is scarcely 2 mm. long but 

 is nearly 7 mm. wide; its anterior margin is nearly straight and little projecting 

 (PI. 160, figs. 3 and J+). The sternum is 24 mm. long, from the posterior margin 

 of the labrum to the subanal fasciole. It is noticeably convex, and just back 

 of its center where it is 18 mm. wide, it culminates in a single point. At the 

 subanal fasciole, it culminates in two points 5 mm. apart. There is thus on the 

 posterior part of the sternum a flat, triangular area, 9 mm. long and 5 mm. 

 wide posteriorly, the corners of which are the three culminating points referred 

 to. The whole sternum is closely covered with tubercles, largest near the 

 margins and smallest at the culminating points. The color of test and spines 

 is very pale brown, the fascioles scarcely darker. The smallest specimen is 

 nearly white. The specimens are all dry. 



The primary spines are for the most part 2 mm. long or less but along the 

 margins of the petals and on the subanal plastron and sternum they are twice 

 that. The largest spines are along the sides of the oral surface of the tesl 

 where they are 5 mm. long. Pedicellariae are not very common and are to be 

 found chiefly near periproct and subanal fasciole. No globiferous, ophicepha- 

 lous, or triphyllous were found. The tridentate pedicellariae have straight 

 narrow valves about .66 mm. long, with dentate margins. The rostrate are 

 more characteristic. The valves (PI. 146, fig. 16) are rather more than half 

 a millimeter long, the base is .25 mm wide but not so high, and the tip of the 

 blade is slightly expanded. 



This interesting new species is based on material from three rather widely 

 separated localities. The figured specimen, a large bare test is from Thuvu 



