Boone, Echinodermata, Cruises of "Eagle" and "Ara," 1921-28 129 



lines converge on the tip of a young spine, giving it also a rough 

 aspect, but in the great majority of primaries this tip is worn smooth. 

 The secondary spines are short, laterally flattened, with fine longi- 

 tudinal ridges separated by fine lines ; the tips of the spines are rather 

 bluntly truncated, or, in some instances, very slightly rounded. The 

 miliary spines of the ambulacral region are elongated while on the 

 interambulacral region they are reduced to papillae. 



The pedicellariae are of three types: (a) The large, globiferous 

 kind which are found principally on the abactinal surface of the inter- 

 ambulacral region. These have a large, terminal aperture with the 

 lip well developed and margins dentate; the blade is curved; the 

 stalk has no limb, (b) The small globiferous kind which are found 

 all over the urchin on the actinostome, ambulacra, interambulacra and 

 the abactinal regions, have a decidedly different appearance from the 

 larger ones. The small ones have a prominent end-tooth on each valve ; 

 the aperture is not terminal and the blade is not curved, (c) The 

 third kind, the tridentate pedicellariae are found most abundantly on 

 the actinal surface of the interambulacra. They have the stalks shorter 

 than the valves which are narrow and somewhat compressed. 



References: Cidaris tribuloides Lamarck, Anim. sans Vert., p. 56, 



1816. 

 References: Cidarites tribuloides Lamarck, Anim. sans Vert., p. 56, 



1816. 

 Cidaris tribuloides Blainville, Diet. Sci. Nat., p. 200, 1830. — A. 



Agassiz, Mem. Mus. Comp. Zool., Ill, part I, Rev. Echini, p. 99, 



1872 (with full synonymy). — A. Agassiz and H. L. Clark, Mem. 



Mus. Comp. Zool., XXXIV, p. 3, pi. 2, figs. 1-4, 1907. 



Order: DIADEMATOIDA. 



Suborder: Aulodonta. 



Family: DIADEMATIDAE. 



Genus: DIADEMA Gray. 

 Diadema setosum (Leske) 1778. 



Plates 83 and 84. 



Type : Leske 's type came from Amboina. 



Distribution : This is one of the best known urchins of the tropics, 

 having a world-wide tropical distribution from Cuba eastward to the 

 Tonga Islands. 



