392 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. xxxn. 



T^Jpe.~C2.t. No. 21217, U.S.N.M. 



On account of the tentacles being- entire!}" retracted, as well as small, 

 it is difficult to compute the number exactly ; 18 were found, but it is 

 entirely probable the number is as high as 20. Crowns of tentacles 

 are of the usual aspidochirot form. The mouth is decidedlj^ ventral 

 when tentacles are retracted. It is encircled in front (but not caudad) 

 by the continuous series of small tubercular papilliform processes 

 which mark the ventro-latei^al ambulacra. Each of these processes 

 is surmounted by one or sometimes two slender papill*. When re- 

 tracted partially they resemble pedicels. There appear to be numer- 

 ous pedicels also, however, as determined by microscopic examina- 

 tion. The absence of any terminal plate in the ambulacral appendages 

 as well as their small size renders any distinction rather risky. In 

 the smaller specimen I was able to make out a number of very small 

 papilliform pedicels along mid- ventral region, where the longitudinal 

 muscle shows through bod}" wall in larger example, but in the latter 

 only a very few exceedingly minute pedicels are discoverable. Scat- 

 tered along either side of the more prominent ventro-lateral pedicels 

 and papilhe are numerous smaller very inconspicuous ones, to be seen 

 readily only with a bright light and a strong glass. No regular 

 arrangement can be made out. Along the two dorsal ambulacra are 

 scattered a few long, very slender papilhe, which appear to form a 

 double row in the anterior portion, at least. Some of these papillas 

 are very thread-like. On account of the difficulty in seeing them it is 

 impossible to give a thoroughly accurate account of their arrange- 

 ment. A few in anterior portion of body, just behind the supraoral 

 collar, are larger than the rest. 



The calcareous ring is a trifle variable and irregular. The dorsal 

 radial pieces seem a trifle heavier than ventral and difter slightly in 

 shape. The component pieces are delicate and readily injured. The 

 form is seen better by figures (Plate LXXII, figs. 2, 2«) than descrip- 

 tion, both dorsal and ventral being shown. Some radial pieces have a 

 slightly more deeply excavated posterior margin, Init, as a rule, it is 

 shallow (fig. %i). Polian vesicle single. Madreporic canal minute, 

 running forward in dorsal mesentery below genital duct; no madreporite 

 was discovered. Ring canal large; proximal portion of radial canals 

 large. No tentacle ampulla, except mere rudiments. Gonad consists 

 of about ten unbranched slender tubes on either side of dorsal mesen- 

 tery, which is more or less perforated in this region. Eggs are fairly 

 well developed, so this specimen is probably mature. Respiratory 

 trees, two, springing from a common base. Longitudinal muscles 

 form a single cylindrical band along each radius. Intestine large, 

 gorged Avith mud and sand. 



The only calcareous deposits are those contained in walls of gonad 

 and respiratory tree. They are irregular ))ranched rods, smooth 



