270 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.48.. 



Color white, integument rather soft, slightly rough to the touch. 

 Pedicels densely distributed all over, especially numerous on ventrum 

 without any serial arrangement except in anal region. Anus is sur- 

 rounded by 5 anal papillae. Tentacles 10, midventral pair slightly 

 smaller than the others. Perforated plates of various sizes forming a 

 thick layer in general perisome. Those situated most superficially 

 (pi. 10, fig. 23) are small and rod-like, usually with a hole at each 

 end, and vary 85-145// in length, averaging 120//. In the deeper part 

 are found larger, smooth plates, 200-400// in diameter, with 15-20 or 

 more holes. Pedicels often passing through a large hole in these 

 plates. There are found all transitional forms between these two 

 sorts of deposits. In the introvert are found scattered, elongated 

 plates of various sizes, with larger holes. Supporting rods of tentacles 

 irregular in form, with minute holes. In pedicels also similar per- 

 forated rods, 90-210// long, are present. End plate well developed 

 in ventral pedicels, measuring 110-150/z in diameter, rudimentary in 

 dorsal pedicels, being only 60-90//. Calcareous ring well developed 

 but devoid of posterior prolongations. Retractors are inserted to 

 body-wall a little anterior to the middle of body length. Polian 

 vesicle and stone-canal single. Genital tubes not branched, few in 

 number. Respiratory trees two. 



Th. spectabilis Ludwig differs from the present species in that the 

 rod-like deposits are thinly scattered and never give rise to perforated 

 plates. Th. articulata Vaney also has similar deposits but differs in 

 having long posterior prolongations in the calcareous ring. The 

 species also resembles Th. unisemita (Stimpson), but differs in the 

 uniform distribution of the ventral pedicels and in the presence of end 

 plates. 



Habitat. — Off Ojika Peninsula, Honshu. 



Type.— Cat. No. 34172, U.S.N.M. 



73. THYONE BICORNIS, new species. 



Plate 10, figs. 24d-d. 



Station 5074. Three specimens. 

 Body fusiform, tapering equally toward both ends; length, exclu- 

 sive of introvert, 26 mm. ; diameter, 11.5 mm. Color gray, with dark 

 brown patches, which are especially abundant in interambulacra. 

 Integument thin, soft and leathery, smooth to the touch. Pedicels 

 very numerous, distributed all over the body, but arranged in a 

 double row in each ambulacrum. Tentacles 10, midventral pair 

 being considerably smaller than the rest. Rather sparsely scattered 

 in general perisome are found table-like buttons (pi. 10, figs. 24a, b). 

 The disk, which measures 40-110// in diameter, with a mean of about 

 70//, has four large primary holes and several peripheral ones, num- 

 bering from 2 to 16. Spire, 25-35// high, consists of two pillars united 



