250 BULLliTIX 76, UNITED STATES NATIONAL MUSEUM. 



spinp, and two subambulacral spines, and from semisqv.amatus in having a much 

 broader disk, shorter ami proximaiiy broader rays, sliorter spinelets on rays, numer- 

 ous inferomarginal peiliccllaria;, and a varial)le number of odd interradial plates. 



BENTHOPECTEN CLAVIGER Fisher. 

 PI. 22, fig. 4; pi. 54, fig. 4; pi. 56, fig.s. 1, ia-b. 

 Benthopecten claviger Fisher, Zool. Anz., vdI. 35, March 29, 1910, p. 548. 



Diagnosis.— R&js five. R = 110 mm.; r=12 mm.; R = 9.1 r. Breadth of ray 

 at base, 14 mm. Disk small, rays long and evenly tapering; interradial angle 

 abrupt. Abactinal surface of disk with numerous conspicuous thorny-surfaced 

 spines which extend upon rays for a short distance, these surrounded at base by 

 eight to fifteen or even more very small thorny spinelets; numerous intermediate 

 plates with one to five tiny spinelets; on ray plates with one to five similar spine- 

 lots forming a fine nap. Interradial odd superomarginal very promment. Abac- 

 tinal pectinate pedicellarise present but usually variable in number. Inferomarginal 

 and actinal adambulacral spines of proximal part of ray club-shaped, the former 

 two, the latter two (sometimes three) in number. Furrow spines four to six, 

 slightly curved. Pectinate pedicellarise between proximal inferomarginals, rarely 

 farther along ray. The most characteristic features of the species are the clavate 

 actinal and inferomarginal spines, the promment thorny disk spines and the 

 extremely delicate abactinal spinelets which often are exceedingly small. Tube 

 feet with small sucking disks. 



Description. — Disk and basal part of rays (papular areas) covered with numer- 

 ous spaced, tapering, blunt, superficially thorny spines, which decrease in size 

 from center of disk outward, ranging from 5.5 mm. to 1.25 mm. in length. These 

 stand on an eminence of plate which is surrounded by eight to fifteen or even 

 more verj^ small, delicate, microscopically thorny spinules or spinelets, ranging 

 from about 0.2 to 0.4 mm. in length. Numerous small intermediate plates bear 

 one to five very tiny spinelets (about 0.2 mm. in length) which cannot be seen 

 without a glass. Plates of ray bear one to five minute sharp, slender spinelets 

 about 0.3 mm. long at base of ray and 0.1 mm. toward tip. These groups of 

 spinelets (often standing on plate in a series) form a sort of fine uniform nap on 

 the abactinal surface of ray. Some of the major spines are slightly club-shaped. 

 Abactinal pectinate pedicellarise are variable in number. Typically they are 

 absent or very few on rays, and few on disk. One specimen from the type-locality 

 has numerous pcdicellariaj along rays, as well as scattered over the disk. Each 

 apparatus is subcircular or elliptical and has two to four robust, but short, papillae 

 in each comb. These blunt comb-spinelets are many times thicker, but only 

 slightly longer than the spinelets of abactinal plates. Each apparatus is from 0.5 

 to 1 mm. in diameter. 



PapuliE extend along ray to about fifth or sLxth superomarginal. There is a 

 small area in center of disk and along each interradial line from which they are 

 absent. On the papular areas the abactinal plates vary greatly in shape with age. 

 In adults they are strongly lobed, the larger with six or seven lobes. The smaller 



