1915.] NATURAL SCIENCES OF PHILADELPHIA. 57 



granulated skin, with several scattered, smooth, hemispherical 

 tubercles on the more proximal shafts; distinctly annulated with 

 hook-bearing segments throughout. Ventral surface of arms 

 entirely smooth. Arm spines, which are present beyond first bifur- 

 cation, very fine and three or four in number at each tentacle pore. 

 Color in alcohol: disk mottled and arms annulated with yellowish 

 and grayish brown. 



One specimen; Sagami Sea. 



This species can be easily distinguished from other species of 

 Astrodadus by the entirely smooth disk covering and by the arms, 

 which are distinctl3^ annulated with hook-bearing segments even 

 at the very base. 

 Astroboa arctos sp. nov. 



Diameter of disk, 65 mm. Distance from centre of disk to inter- 

 radial margin, 25 mm. Distance from outer end of oral slit to first 

 bifurcation, 32 mm. Arms branched about thirty-seven times, 

 measuring approximately 420 mm. in total length. Width of 

 ventral surface of arm base within disk, 17 mm. 



Disk decagonal, with concave interbrachial and brachial borders, 

 the former being longer and more concave than the latter; very high 

 and convex, but with more or less depressed central region, covered 

 by a thick skin, which is shagreened by the presence of very fine, 

 close-set granules. The granules are smooth, not acute, irregular 

 in size, when viewed under a microscope, the coarser ones being 

 more numerous on the radial ribs than in the intercostal spaces. 

 Radial ribs long, narrow, bar-like, widest at outer end, suddenly 

 narrowed for a very short distance, then uniformly tapered inwards, 

 nearly reaching disk-centre. Ventral interbrachial areas covered 

 by thick, apparently smooth skin, which, however, contains fine 

 microscopical granules. Genital slits rather large, adradial border 

 protected by a cluster of close-set spinules. 



Madreporic shield, situated at inner angle of a ventral inter- 

 brachial area, more or less semilunar, with semicircular inner, and 

 distinctly notched outer, side and rounded lateral angles. Areas 

 proximal to ventral interbrachial regions, apparently smooth, but 

 ■closely covered with very fine granules of microscopic size, the 

 granules being rather coarse and distinct at the oral angles. Teeth 

 and papillae very numerous; oral and dental papillae, rather small, 

 spiniform, and not very acute; teeth, much larger and longer than 

 papillae, distinctly spatulated, and flattened at tip. 



Two main stems, outside the first bifurcation, of an arm are not 



