226 HAWAIIAN AXD OTHER PACIFIC ECHINI. 



The "lantern" of Glyptoeidaris (PI. 90, figs. 7-9) is remarkably like that of 

 Arbacia. The teeth are strongly keeled, the jaws are very erect, the foramen 

 magnum is deep and the epiphj-ses do not meet above it. Unlike Arbacia, but 

 like Stomopneustes, the top of each half-pyramid gives rise to a process extend- 

 ing down on each side of the tooth giving support to the latter. These proc- 

 esses are not from the epiphyses. One is well shown in fig. 7, PI. 90, but in 

 figures 8 and 9 this important character is not clearly indicated. The pits 

 beneath the epiphyses, characteristic of the Centrechinoida, as recently shown 

 by Jackson (1912, Mem. Boston Soc. Nat. Hist., VII, p. 178, 183) are 

 remarkably large and deep. The perignathic girdle is similar to that of -Arbacia, 

 the auricles being more or less in contact but the apophyses between them 

 being inconspicuous. Unlike Arbacia the primordial interambulacral plate is 

 resorbed. 



The alimentary canal (PL 90, figs. 5, 6) is surprisingly like that of Centre- 

 chinus. There is a very long oesophagus followed by a capacious and much 

 folded intestine, the loops of the upper coil alternating with those of the lower. 

 The anus lies to the right and a little behind the centre of the periproct, and a 

 small but distinct suranal plate is evident on the opposite side. The right 

 posterior ocular plate is in contact with the periproct but all of the others are 

 excluded, in all of the five specimens examined. 



The buccal membrane carries, in addition to the five pairs of buccal plates, 

 numerous sm.aller plates, many of which carry spines as well as pedicellariae. 

 The gill-slits are neither deep nor conspicuous, though the gills are well devel- 

 oped. Rudiments of Stewart's organs are obvious on the sides of the lantern- 

 membrane, below the ends of the compasses. 



The Spines, PEDicELLARiiE, Sph.eridia, and Spicules. 



Plate 92, figs. 1-11. 



The spines are long, slender, and pointed, and the primaries arc especially 

 conspicuous. The surface of tlio spines is veiy smooth, while the inner structure 

 is \ (M y compact and, to a certain extent, resembles that of some Arl>acia spines. 

 (See Mcintosh. 1SS3. Trans. Roy. Irish Acad., XXVIII, p. 255, PI. 8, fig. 32.) 

 The tubercles are all imperforate and the larger secondaries as well as all the 

 primaries are very markedly crenulated. The boss is very high and the scro- 

 bicule is nearly or quite flush with the surface of the test. 



The pedicellaria? of Glyptoeidaris are very characteristic. They have been 



