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 pedicellariae 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 

 pedicellaria; occur in the same two forms which were referred to under mirahilis; 

 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 

 com])letely with the tridentates. The iriphyllous show no peculiarities; the 

 valves are .10 -.13 mm. long. — The 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 ])lates are dcc\) brownish rose. The jieriproct is wiiite. The large 

 primaries luv light green (ne;;r no. 2S() K. & V.) at base, dull rose-red (near no. 

 17 K. t^' V.) on llie dislMl half and light, almost or cjuite white, at tip. Tlie 

 anil)ula('ral i)riinan(^s and all the secondaries are white. The actinal inter- 

 ambulacral piiiuarics ai"e iu>arly oi* (juile white with one or two bands of redilish. 



Were it not for th(^ fact tliat the outline of the test is circular, this i)eautiful 

 sea-urchin would lu^ easily mistaken for an Iv'hinonietra. the short stout pri- 

 maries are so suggest i\e of that g(>nus. It is obvious however that it has no near 



