394 BULLETIN 100, UNITED STATES NATIONAL MUSEUM. 



median radial plates and 2 parallel series on either side lack gran- 

 ules on the transverse margins, those on the lateral margins being 

 correspondingly enlarged and acting as an opercular cover to pro- 

 tect the underlying papulae. The other plates, of which the pri- 

 mary basals are largest, are bordered by a complete series of small 

 oblong granules flush with the surface, those at the corners more or 

 less enlarged and opercular. The surface of the plates is rough- 

 ened by numerous uniform, spaced, low, minute, blisterlike bosses, 

 the same occurring on the central portion of the marginal plates. 

 Madreporic body surrounded by 3 plates. From the coelomic side 

 the plates are flat and have 6 truncate lobes which meet but do not 

 overlap those of neighboring plates, the lateral lobes being best 

 marked, that on the distal and proximal margins being shorter, 

 often incipient. Papulae G about a plate. Superomarginals 14, the 

 third meeting its fellow medially (sixth in Doderlein's Thursday 

 Island specimen; see 1896, pi. 18, fig. 33). These first 3 plates are 

 of nearly uniform width; they do not increase in size as in Litho- 

 sonia and Astroceramus (usually). Each interradial pair of plates 

 is dark brown, while others irregularly along the ray are similarly 

 colored. Actinal intermediate plates surrounded by flat granules 

 and arranged in 3 chevrons with 1 or 2 extra plates next to margin 

 interradially. 



The adambulacral armature consists of granules graded in 

 size from outer margin to the 4 short, blunt, subprismatic, almost 

 granuliform furrow spines. The latter are in curved series, the 

 distal end overlapping the proximal end of the succeeding series. 

 Back of these are 2 crowded series of 3 or 4 granules each; then 

 (on the proximal plates) a small oval bare spot, followed, on the 

 outer part of plate, by 5 or 6 small granules like those of the inter- 

 mediate plates. The subambulacral spines do not become enlarged 

 and tubercular on the outer part of the ray as in Astroceramus and 

 Lithosoma. The granules of the mouth plates also have the closely 

 banked arrangement, 7 or 8 standing on margin, and the inner only 

 a trifle enlarged. There is no sign of any pedicellariae on the 

 specimen. 



Distribution. — East Indies and northern Australia : Malacca, Bil- 

 liton, Jolo, Aru Islands, Thursday Island (off Cape York, Aus- 

 tralia), Percy Island (Queensland). 



&-pecimen examined. — Station 5174, 2.G miles west of Jolo Light, 

 Jolo, Sulu Archipelago, 20 fathoms, coarse sand; surface tempera- 

 ture, 82° F. 



Remarks. — In a recent paper on Australian echinoderms. Dr. H. L. 

 Clark, 1916, p. 36) contends that this species should be called Dori- 

 gona longimana for the following reasons: Dorigona as diagnosed 

 by Gray in 1866 included two species — D. reevesii and D. longimana 



