388 BULLETTN" 100, UNITED STATES NATIONAL MUSEUM. 



Genus OPHIDIASTER Agassiz.' 



Ophidiaster Agassiz, M6m, soc. sci. nat. Neuchatel, vol. 1, 1835, p. 191, 

 Type, O. opMdianus (Lamarck). 



KEY TO SPECIES OF OPHIDIASTEE HEREIN DESCBIBED. 



a\ Center of some of the abactinal and marginal plates with 1 or more en- 

 larged, tuberculate granules, or with single tubercles, or spines. 

 6*. Adambulacral armature in 2 series, the subambulacral spine of irregular 

 occurrence; marginal and abactinal plates with conspicuous central 



spine, or serial tubercles fuscus, p. 388. 



6'. Adambulacral armature in 3 series. 

 c*. Papulae normally in 6 longitudinal series; plates with single central 

 tubercle ; sheath of pedicellariae with margin of depression entire, 

 not toothed or crenulate; papular areas large (except in young speci- 

 mens) with 10-12 pores tuberifer, p. 393. 



c*. Papulae in 8 longitudinal series ; plates with several enlarged tubercu- 

 late granules ; sbeath of pedicellariae with crenulate or toothed 



margin; papular areas small, with 3 or 4 pores trychnus, p. 390. 



a^ Abactinal and marginal plates covered with a fine granulation without a 

 sign of central tubercles or spines ; adambulacral armature in a double 

 series on furrow, but the regular subambulacral spine lacking except in 

 a rudimentary condition at end of ray dtibiosus, p. 394. 



OPHIDIASTER FUSCUS (Gray). 



Plate 95, figs. 5, 5a-c ; plate 103, fig. 4 ; plate 104, fig. 1 ; plate 111, figs. 5, 6. 

 Tmnaria fusca Gkay, 1840, p. 283 ; 1866, p. 13. 

 Ophidiaster fuscus Perkier, 1875, p. 132. 

 Linckia megaloplax Bell, 1884&, p. 126. 



I made some notes and sketches of Gray's type and the specimens 

 listed below appear to be fairly typical examples. The species is 

 somewhat variable. In most cases the color is a striking combina- 

 tion of " Bougainvillea " purple and brown. The accompanying de- 

 scription and figures will probably be useful for a comparison with 

 nearly related forms, O. hirsutus Koehler, for example. 



Description. — General appearance very similar to that of 0. hir- 

 sutus. The abactinal and marginal plates are strongly convex and 

 form 7 regular series. The granules are smallest around the border 

 of plates, increasing in size toward the center, where they are unequal, 

 some of them being more convex than others. The granules of the 

 papular areas are unequal in size, some being subequal to the gran- 

 ules of the borders of the plates, others 2 or 3 times as large. The 

 center of the abactinal and marginal plates bears either a stout coni- 

 cal spine or a spine with 1 to several tubercular granules at the base, 

 or some plates may bear 2 to 5 tubercles shorter than the spines. The 

 largest specimen from station 5641 is remarkable for having on prac- 

 tically all the abactinal and on many of the superomarginal plates 

 as well a heap of upward of 9 or 10 unequal subconical or acorn- 

 shaped, enlarged granules instead of the spine. Most all the infero- 



* Chione Gistel, Naturgeschlchte des Thlerrelchs, 1848, p. 176. Type, Chione ophidianua 

 (Lamarck). 



