238 BULLETIN 88, UNITED STATES NATIONAL MUSEUM. 



Gregory comments on this genus as follows : 



" Palasopliiuridae in which the ambulacral ossicles are subhep- 

 tagonal in form, the central suture along the arm being zigzag, while 

 the outer angles of the ossicles are cut away for the reception of the 

 podia. The adambulacral ossicles have a flat base, and thence bend 

 forward crescentically. The mouth frames are massive, and those 

 of each pair meet along the middle line of the oral angle. 



"This genus I only know from Prof. James Hall's figures, and, in 

 spite of theii- clearness, I feel much doubt as to the wisdom of diag- 

 nosing it from these alone. Its affinities are clearly with the Palae- 

 ophiuridse, but it approaches the Protasteridse in one respect, for, 

 owing to the deep depressions in the outer angles of the ambulacral 

 ossicles, the outer side forms a short rudimentary wing. The genus 

 differs from all the Protasteridse by the absence of a muscular groove 

 across the ambulacral ossicles. 



''Among the Pala3ophiund8e it differs from PalxopTiiura by the 

 absence of marginal ossicles, and from Sturtzura and Tseniura by 

 the massive nature of the mouth frames." 



Contains : 



E. logani (Hall). Hamilton. 



E. {f) concinna (Rmgueberg). Rochester. 



EUGASTERELLA LOGANI (Hall). 



Eugaster logani Hall, Twentieth Rep. N. Y. State Cab. Nat. Hist., 1868, p. 290; 

 rev. ed., 1868=1870, p. 333, pi. 9, figs. 7, 8. 



Original description. — "Body stellate, with a small disk and long 

 atteimate Hexuose rays. Disk composed of numerous small poly- 

 gonal plates with radiated surfaces; the diameter, measured from the 

 sinus to its extension on the opposite ray, is about haff as great as the 

 length of the ray measured from the center of the disk. Rays, as seen 

 from the ventral side, narrow, attenuate, with the ambulacral plates 

 curving, and near the base of the rays a little wider than long, and 

 toward the extremities longer than wide, with a strong elevated 

 transvei-se ridge. There are about eight pairs of plates inclosed 

 within the limits of the disk. Pores penetrating the intei-stices 

 near the outer extremities of the plates, while near the inner end there 

 is a depression or pit resembhng a partially excavated pore. The 

 adambulacral plates as seen from below are extremely narrow and 

 very convex on their outer surfaces, forming the mai-gins of the ray. 

 Oral plates in pairs, narrow and elongate. 



"This specimen measures, from the center of the disk to the extrem- 

 ities of the rays, about one inch and a haK; the widest part of the ray, 

 which is near the margin of the disk, is about an eighth of an inch 

 in diameter. The rays toward then* extremities have the ambula- 

 cral field covered by the curving of the mai-ginal plates over the 



