224 HAWAIIAN AND OTHER PACIFIC ECHINI. 



the primordial plates. The gills are small and their slits insignificant. The 

 auricles are moderately high but widely separated, showing no tendency to meet. 



The primary tubercles, especially those above the ambitus, in the inter- 

 ambulacra, are very large, with disproportionately large, perforated mamelons. 

 Of the secondary tubercles, only one or two are perforated. There is not the 

 least trace of crenulation on any of the tubercles. The primary spines are very 

 conspicuous, at least those on the uppermost three or four interambulacral plates 

 in each column. These measure from 12 to 22 mm. in length and from 1 to 2 mm. 

 in thickness; the thickness is from .06 to .15 of the length but is usually less 

 than .10. All the spines taper to a blunt point, the large ones rather abruptly, 

 the small ones gradually. They are very finely and uniformly striated longi- 

 tudinally but are quite smooth. All are perfectly solid throughout. 



Pedicellarise of all kinds are fairly common. The globiferous are not con- 

 spicuous, for the glands are light brown, not dark brown or purple as in the other 

 species. Their valves (PI. 91, fig. 18) terminate in two slender teeth, remarkable 

 for their length. The tridentate pedicellarise are very variable, the valves rang- 

 ing from .20 to 2 mm. in length; they are sometimes broad and flat (PI. 91, fig. 

 19) but are usually narrow and compressed, and may be either straight and in 

 contact for some distance or curved and meeting only at tip. The ophicephalous 

 pedicellarise occur in the same two forms which were referred to under mirabilis; 

 the characteristic forms are remarkable for their very narrow valves (PI. 91, fig. 

 20), which are about .30 mm. long, including the loop; the other form intergrades 

 completely with the tridentates. The triphyllous show no peculiarities; the 

 valves are .10 -.13 mm. long. Tlie sphceridia (PI. 91, fig. 22) are somewhat 

 elongated but show no characteristic features. The calcareous spicules of the 

 tube-feet (PI. 91, fig. 21) are remarkable only for being finely spiny on their 

 convex surface. 



The coloration of this species, as shown in the alcoholic specimens, is un- 

 usually handsome. The test is white actinally, becoming rosy above; the genital 

 and ocular plates are deep brownish rose. The periproct is white. The large 

 primaries are light green (near no. 286 K. & V.) at base, dull rose-red (near no. 

 17 K. & V.) on the distal half and light, almost or quite white, at tip. The 

 ambulacral primaries and all the secondaries are white. The actinal inter- 

 ambulacral primaries are nearly or quite white with one or two bands of reddish. 



Were it not for the fact that the outline of the test is circular, this beautiful 

 sea-urchin would be easily mistaken for an Echinometra, the short stout pri- 

 maries are so suggestive of that genus. It is obvious however that it has no near 



