208 BULLETIN 100, UNITED STATES NATIONAL MUSEUM. 



feromarginal spine and of inferomarginal pedicellariae are addi- 

 tional differences separating tHplaeantKus from granulatus. Ch. suh- 

 tuberculatus was taken by the Challenger at station 164, off the 

 coast of Australia, east of Sydney, 950 fathoms, green mud ; bottom 

 temperature 36.5° F. 



Genus BENTHOPECTEN Verrill. 



BentJiopecten Verkill, Amer. Journ. Sci. and Arts, vol. 28, 1884, p. 218 

 (footnote).— LuDwiG, 1910, p. 464 (part).— Fisher, IQlld, p. 142. 

 Type, B. spinosus Verrill. 



Parachaster Sladen, 1885, p. 610.— Ludwig, 1910, p. 462 (part). Type, 

 P. pedicifer Sladen ; figure. 



KEY TO SPECIES OF EENTHOI'ECTEX HEREIN DESCRIBED. 



a\ Actinal plates with a single spinelet, the long spines of disk graduated in 



length into spinelets of ray B. moluccanus, p. 208. 



a'. Abactinal plates with more than 1 spinelet, at least on dislv ; the compara- 

 tively few prominent spines of ray not graduated in length into those 

 of disk. 

 h^. Abactinal plates of ray with upward of 5, or even more, .spinelets; odd 

 interradial superomarginal spine not unusually long (equal in length to 

 first 1.5 to 2 superomarginals) ; short acce.ssory superomarginal spines; 



inferomarginal pedicellariae on outer part of ray B. polyctenius, p. 211. 



h'. Only 1 or 2 spinelets to each abactinal plate of ray ; odd interradial 

 superomarginal spine very long (equal in length to first 4 or 5 supero- 

 marginals) ; no accessory supei'omarginal spines; no inferomarginal 

 pedicellariae on outer part of ray B. styracius, p. 213, 



BENTHOPECTEN MOLUCCANUS Fisher. 



Plate 53, fig. 1 ; plate 55, figs. 5, 5a-&. 

 BentJiopecten moluccanus, 1913c. p. 207. 



Diagnosis. — Differing from B. hvddlestonii in having only 2 in- 

 feromarginal and 2 subambulacral spines, and from B, acanthonotus 

 in having a larger adambulacral furrow comb (with 7 to 9 spines), 

 pedicellariae between the distal inferomarginal plates, very few or no 

 accessory abactinal spinelets, a more restricted papular area, and in- 

 feromarginal spines which are subequal proximally. K=80 mm., 

 r=8 mm., R=10r; breadth of ray at base, about 10 mm. Disk 

 small, rays slender and very flexible. Abactinal plates with a single 

 spine, those of disk graduated in length into spines of rays ; supero- 

 marginals with 1 and inf eromarginals with 2 spines ; subambulacrals, 

 2 ; furrow spines, 7 to 9 ; oral spines variable, 5 to 8 ; suborals, 3 to 5 ; 

 abundant abactinal pedicellariae on disk and variable on rays; in- 

 feromarginal pedicellariae in interbrachium and an outer part of 

 ray; actinal intermediate pedicellariae often present. 



Description. — Abactinal plates each with a single, slender, thorny 

 spine, those of the disk long and bristling (4 mm., or equal in length 

 to 1.5 proximal superomarginals). These shorten gradually from cen- 



