Boone, Echinoidea, Cruise of "Alva," 1931 257 



The tridentate pedicellariae are quite numerous and are of 

 two types, the large ones being very elongate, slender, with the 

 head 1.5 to 1.7 mm. long, the valves meeting on the distal half of 

 their margins. The small, tridentate pedicellariae are formed of 

 leaf-like blades. A few globiferous pedicellariae are present, 

 mostly located on the actinal area. These contain many bihamate 

 spicules. 



References: Parasalenia gratiosa, Agassiz, A., Bull. Mus. 

 Comp. Zool., vol. I, 1863, p. 22; Mem. Mus. Comp. Zool., vol. 

 VII, pt. Ill, pi. 3d, figs. 1 and 2.— DE Meuere, J. C. H., 

 "Siboga"-Expeditie, Echinoidea Monogr. 53, Livr. 14, 1904, 

 p. 97 (extensive reference list). — Mortensen, Th., K. 

 Danske Vidensk. Selsk. Skrifter Nat. og Math., 7 E R 1, 1906, 

 p. 121, pi. 5, fig. 36. — Clark, H. L., Mem. Mus. Comp. Zool., 

 vol. XXXIV, 1912, p. 369; Publ. 214, Carnegie Inst. Wash., 

 Dept. Mar. Biol. Papers, 1921, p. 150; Catalog Recent Sea- 

 Urchins B. M. N. H., 1925, p. 141. 



Genus: ECHINOMETRA Rondel 1554 

 Echinometra mathaei de Blainville 



Plates 93 and 94 



Type: De Blainville's type, which is in the Paris Museum, 

 came from the Indian Ocean. 



Distribution: This small sea-chestnut is gregarious and 

 abundant in the reef-dwelling fauna of the vast Indo-Pacific 

 region. It has been reliably reported from the Gulf of Suez, Egypt 

 and the Red Sea, eastward through the Persian Gulf, the Indian 

 Ocean, north to Japan, and southward to the east African coast, 

 and eastward in the Philippines, New Guinea, Australia, Poly- 

 nesia, the Society Islands and the Hawaiian Islands. 



Material examined : Ten specimens from Venus Point Reef, 

 Tahiti, Society Islands, August 15, 1931. Four small specimens, 

 in coral, Teviatoa Reef, Raiatea Island, Society Islands, August 21, 

 1931. 



Technical description : The test of E. mathaei is thick, with 

 the height usually between 55 and 65 per centum of the length ; 

 the abactinal system is from 15 to 25 per centum of the length, 

 and the width of the test is from 65 to 75 per centum of the length. 



