290 BULLETIN 82, UNITED STATES NATIONAL MUSEUM 



The extraordinarily developed comb on the oral pinnules, combined with the 

 presence of prominent spinous knobs or keels on the earlier brachials, at once distin- 

 guish this species from all others. 



While it is scarcely possible to confuse this form with any other of the Comas- 

 teridae, its central mouth, its sacculi, its very small size and delicate build, and espe- 

 cially the fact that the division series and arm bases are closely appressed with the latter 

 parallel to each other and to the dorsoventral axis, give it an appearance quite unlike 

 that of any other comasterid, but much resembling that of many of the smaller forms 

 among the Antedonidae, and it is very likely to be mistaken for some member of 

 this family until the oral pinnules are examined. 



Description. The centrodorsal is hemispherical, almost completely covered with 

 closely crowded cirrus sockets. 



The cirri are about XL, 17, about 13 mm. long, fragile and deciduous, though 

 not excessively slender. The apical cirri are markedly shorter and weaker than the 

 peripheral and are composed of 14 segments. The 2 basal segments are short, the 

 third is longer, and the fourth-eighth are much elongated. The fifth and sixth are 

 the longest, nearly or quite three times as long as broad. The elongated segments 

 are somewhat constricted centrally. Beyond the eighth the segments gradually 

 decrease in length and become strongly compressed laterally. The third from the 

 last is not longer than broad. The short distal segments have very slight terminal 

 dorsal tubercles, and the opposing spine is well developed. 



The radials are visible beyond the centrodorsal as narrow bands. The IBri are 

 short and are deeply incised distally by a rounded proximal process from the axillary 

 which rises to a low broad and well-rounded synarthrial tubercle. The IBr 2 (axil- 

 laries) are rhombic, with a slight median groove in the distal portion and strongly 

 concave distal sides. 



The 10 arms are up to 50 mm. in length. The first brachials are short, longer 

 exteriorly than interiorly, and are much incised by a rounded posterior process from 

 the second which rises to a broad and well-rounded synarthrial tubercle. The 

 second brachials are rhombic with a strong posterior process. The first syzygial 

 pairs (composed of brachials 3 + 4) are about as long as the second brachials and 

 cylindrical. The fifth brachial is of the same length, slightly wedge-shaped, the 

 sixth is pronouncedly wedge-shaped and somewhat longer, and the seventh and 

 eighth are similar to the sixth. The second syzygial pair (composed of brachials 

 9 + 10) is longer. The succeeding brachials, especially from the fourteenth onward, 

 are triangular, except for the syzygial pairs, which are always elongated and trape- 

 zoidal. From the fifth to the eighth the brachials bear dorsally a knoblike or bluntly 

 carinate process which is beset with exceedingly fine spines. The surface of the 

 preceding and also of the succeeding brachials is everywhere smooth. 



Syzygies occur between brachials 3 + 4, 9 + 10, 14 + 15, 18+19, 22 + 23, 26 + 27, 

 and 30 + 31, sometimes between brachials 13 + 14, 17+18, and 22 + 23. 



Pj is composed of about 35 segments, of which the 4 basal are irregularly rhombic, 

 being produced into a point dorsally, and are in contact only in the middle of their 

 ends. The following segments are about as long as broad, increasing in width 

 distally so that they overlap the base of the succeeding segment both dorsally and 



