148 



ART. 2. — H. IMATSUMOTO 



boss. The second radiais and the first to third interradials may 

 also be distinguished, and are large and prominent. Thus, the 



disk squamation is rather similar 

 to that of Opliiozona. Eadial 

 shields comparatively small, 

 oblong ovate, about two-fifths 

 as long as the disk radius, 

 twice as long as wide, wider 

 without, more convex abradially 

 than adradially, separated from 

 each other by a row of three 

 or four plates, of which the 

 inner ones are larger. In each 

 interradial space, there are five 

 to seven ii'regularly radiating 

 rows of scales. Interbracliial 

 ventral surfaces covered with 

 coarse, irregular, imbricating 

 scales. Genital slits long, near- 

 ly reaching the margin of the disk. Genital scales invisible. 



Oral shields small, rhomboidal, with acute innei' and rounded 

 lateral and outer angles, and shghtly concave inner sides. Adorai 

 shields wider without, nearly or quite meeting within. Four oral 

 papilla) on either side of the oral angle, inner ones smaller and 

 more acute. Deep in the oral slits, on either side of the oral 

 angle, there occurs one long, acute, needle-like papilla. Five teeth, 

 all blunt, except the uppermost one, wliicli is pointed. 



Five arms, slender, flattened, uniformly tapered toward the 

 extremity. Dorsal arm plates large, fan-shaped, twice as wide as 

 long ; inner sides slightly convex and forming an obtuse angle 



Fig. 36. Amphiartls wnhonata. x8. a. 

 From above. J>. From below, c. Side view 

 of two firm joints near disk. 



