98 BULLETIN 100, UNITED STATES NATIONAL MUSEUM. 



hawaiiensis, tapered, slightly curved, and Avith the characteristic 

 thorny tip of hawaiiensis, only more delicate. The second or third 

 lateral spine from the upper end is the longest, equaling in length 



2 superomarginals. The underlying spines of the second lateral 

 series are about as long, but more delicate. All are closely appressed 

 to the side of the ray. The rest of the plate is covered with terete 

 round-tipped spinelets similar to those of hawaiiensis. On the me- 

 dian line at the inner end of most of the inferomarginals of ha- 

 waiiensis is an enlarged spinule, which does not form a part of the 

 transverse series. This is only rarely present in diploctenius. At 

 about the middle of the actinal surface of a majority of the plates of 

 diploctenius is a fascicular pedicellaria formed of several unmodified 

 spinelets. I have not been able to find these in hawaiieiisis. A por- 

 tion of the description of the inferomarginals of haioaiiensis needs 

 modification. It is stated (Fisher, 1906, p. 1015) that the actinal 

 inferomarginal spines are blunt; they so appear in alcoholic speci- 

 mens, but when dried the tips are thorny and as in plate 3, fig. lb 

 (ibidem). The curious hooked tips of the inferomarginal spines 

 and spinules seem to be generic, but the membrane hides the hooks 

 in the case of the actinal spines. 



Adambulacral plates with fewer subambulacral spines than in 

 hawaiiensis and with frequent fasciculate subambulacral pedicellariae. 

 Furrow spines 3, blunt, long, slender, and compressed, the median 

 the most. Subambulacral spines often 'in 2 longitudinal series of 



3 each, with 1 to 3 shorter spines on the outer part of plate; or 

 proximally the outer series, and sometimes also the inner, may have 



4 spines. These are all tapering, slender, and blunt, those of inner 

 row a little longer than furrow spines. The pedicellariae are of 

 frequent occurrence and usually stand on the aboral inner corner 

 of the plate. Each consists of about 5 tapering spines surrounding 

 a pit in the plate. The aboral spine of the first actinal series some- 

 times stands on the furrow margin. This is regularly the case in 

 hawaiiensis so that there appears to be 4 furrow spines, or 5 when 

 the adoral member moves also to the margin. The actual number of 

 furrow spines is only 3 in both species. First adambulacral plate 

 compressed with about 15 spines in 2 transverse series. 



Mouth plates densely covered with spines, the armature being 

 similar to that of hawaiiensis. At inner end of plate are 4 heavy, 

 blunt teeth forming a perpendicular comb (a part of the superficial 

 series), which is continued to the outer end of the narrow plates, 

 adjacent to median suture in about a dozen more, much slenderer, 

 tapering, blunt spines, which become smaller as they approach the 

 outer end of the plate. The actual marginal spines are small and 



