402 BULLETIN 100, UNITED STATES NATIONAL MUSEUM. 



marginal plates actinal in position, separated from adambulacrals 

 over most of ray by a single series of actinal intermediate plates, 

 and on disk by small plates in transverse series; actinal interradial 

 areas small ; papulae single in the small interspaces between abactinal 

 plates; plates convex and armed with a group of short, blunt, spine- 

 lets resembling parapaxillae or pseudopaxillae, 15 to 20 to a plate; 

 marginal and actinal spinulation compact ; adambulacral plates small 

 with slightly curved furrow margin ; spines small, crowded, grading 

 into actinal spinulation; proximally 5 or 6, distally 3 or 4 furrow 

 spines, with 2 to 4 crowded series each of 2 or 3 subambulacral spines. 

 Well-developed superambulacral ossicles ; ampullae double ; tube feet 

 rather small, with well- developed sucking disks. 



Remarks. — It is difficult to place this genus. The presence of 

 double ampullae, closely placed and regularly imbricated plates, and 

 presence of superambulacral ossicles debar it from the Echinaster- 

 idae. The two other available families are the Ganeriidae and Aster- 

 inidae. While Tarachaster resembles Nephantliia superficially, on 

 account of the radial zone of irregularly arranged plates, I think its 

 relationships are more with the Ganeriidae. Superambulacral ossicles 

 have not been reported in either the Ganeriidae or Asterinidae. The 

 imbricated pseudopaxillae, with definite lobes, the definite but not 

 particularly conspicuous marginals, the actinal intermediate plates 

 in transverse columns, and the character of the adambulacral arma- 

 ture are not dissimilar to these features in the Ganeriidae. The 

 slender rays and very reduced actinal interradial areas are new to 

 the Ganeriidae, but in the Asterinidae a parallel case is found in 

 Nepanthia, where the character varies within the genus. But Tara- 

 chaster does not seem to me to be closely related to any known genus 

 of the Ganeriidae. The superambulacral plates remain something 

 of a problem. 



TARACHASTER TENUIS Fisher. 



Plate 41, figs. 7, 7a; plate 120, fig. 4; plate 121, fig. 3; plate 126, fig. 1. 

 Tarachaster tenuis Fishee, 1913e, p. 216. 



Diagnosis. — Eays 5. R=67 mm., r=12 mm., R= 5.5+r; breadth of 

 ray at base 14 mm.; rays depressed, rather slender, long, bluntly 

 pointed ; disk small ; sides of ray rounded and occupied by the abac- 

 tinal plates; abactinal plates small, those on disk and along radial 

 area of ray irregularly three-lobed, imbricating ; dorsolateral, lateral, 

 and narrow portion of ventral surface occupied by four-lobed plates 

 in about 10 longitudinal series at base of ray, also forming transverse 

 series; 3 series of larger plates adjacent to adambulacrals, the outer 

 two being the marginals; plates covered by small, stout, upright, 

 round-tipped, often clavate, close-set spinelets in groups resembling 



