712 PROCEEDINGS OF THE NATIONAL MUSEUM. 



VOL. XXXU. 



KEY TO HAWAIIAN SPECIKS OF THYONIDIUM. 



a Pedicels scattered all over body; no tables in pedicels hawaiiense. 



aa Pedicels in double rows along ambulacra of trivium, absent from ventral inter- 

 ambulacra; pedicels crowded with modified tables alexancJri. 



THYONIDIUM HAWAIIENSE, new species. 

 Plate LXXIX, figs. 2, 2a-e. 



Size small; general form subglobose, tapering ver\' slightl}- toward 

 either end, and abruptly narrowed at the neck; no conical caudal por- 

 tion; contour of bod}- very broadly elliptical; if neck and tentacles 

 were eliminated, animal would resemble a large papillose gooseberry. 

 Tentacles, five pairs of large, alternating with five pairs of very much 

 smaller ones; only six large tentacles remaining, two pairs apparently 

 haying been scraped off. Pedicels numerous and scattered, but slightl}" 

 more numerous on trivium and there arranged in irregular rows, 

 especially at either end of body; the median line of either ventral 

 interambulacrum nearly free from pedicels, thus forming an incon- 

 spicuous narrow naked band. Perisome minutely roughened by spires 

 of tables. Deposits: Tables with a rather symmetrical, subcircular 

 smooth disk pierced by four larger and four smaller alternating per- 

 forations; spire composed of two rods, a crossbeam at bottom and 

 near summit, the crown ending in two or four teeth, sometimes irreg- 

 ular with three. At base of tentacles disks of tables elliptical, with 

 four larger central holes and many (fifty or more) smaller perfora- 

 tions, the spire often solid or nearl}" so, ending in two or three teeth. 

 No tables in pedicels, the latter having well-developed terminal plates. 

 Color in alcohol, violet gray, the pedicels and tentacles brownish. 

 Length, 21 mm.; width, 12 mm. 



Locality. — Station 4101, Pailolo Channel between Maui and Molokai 

 islands, 143 to 122 fathoms, coral sand, shells, foraminifera; bottom 

 temperature, 59.7°; 1 specimen. 



Type.—Q^t. No. 21223, U.S.N.M, 



The smaller tentacles are inconspicuous, being only about 1.25 mm. 

 long, while the larger are about 4 to 4.5 mm. The former correspond 

 to the radii, the latter to the interradii. Perisome is moderately thin 

 and rather translucent, though not markedly so. Calcareous ring is 

 very large compared with size of animal, being about 13 mm. long. 

 Radial pieces have posterior prolongations which are rigidly fused 

 with posterior portion of interradial pieces, both being composed of 

 numerous smaller polygonal component plates. Anterior portion of 

 radial pieces fairly solid; figure will show form of pieces. One small 

 madreporic canal and one Polian vesicle. Respiratory trees rather 

 small. Tubules of gonad once or twice dichotomously branched and 

 containing well-developed eggs. 



