4 8 NATURAL HISTORY BULLETIN. 



portions are ovate or elliptical, nearly parallel, and separated 

 by several rows of scales and granules. They appear to ex- 

 tend but little beyond the exposed parts. 



Upper arm-plates, except the basal ones, are rhombic or 

 nearly lozenge-shaped, with a slightly angulated prominence 

 in the middle of the outer margin, corresponding to a low 

 median ridge; lateral margins slightly convex; proximal end 

 angulated. slightly separated by the lateral plates. They are 

 broader than long. 



Under side of disk covered with minute, exposed scales, 

 with few granules. Oral shields about as long as wide, 

 rather rhombic, with rounded side angles, and a more promi- 

 nent inner angle; the outer end projects slightly into the in- 

 terradial area-; the sides do not touch the side arm-plates. 

 x\doral shields are long, narrow, irregularly trilobed, the dis- 

 tal end, embracing the lateral corners of the oral shield and 

 touching the first under arm-plate, separates the latter from 

 the oral shield. 



Outer oral tentacle-pore large and exposed on the edge of 

 the jaw, bordered by some small papillae. Oral papillae small, 

 conical, acute, numerous, about seven to twelve on each side 

 of a mouth-slit, of which four to seven form a proximal marg- 

 inal row;-others, in the largest specimens, lie within the slit, 

 above and around the large tentacle-pore; those next the tip 

 of the jaw are the largest. Several others (about 4 to 6 in 

 the larger specimens) form an irregular row below the oral 

 tentacle-pore, on the surface of the jaw. In the younger 

 specimens there are about three in a regular row. Tooth- 

 papillae two, spiniform, situated at the edge of the dental 

 plate. Teeth stout, flat, five or six. 



Under arm-plates, except a few basal, irregularly traper- 

 zoidal or broad shield-shape, about as wide as long; the distal 

 end broadly rounded; lateral edges strongly incurved; inner 

 end very obtusely angled; scarcely separated by the lateral 

 plates, except the two or three basals. Beyond the middle of 

 the arm they become oblong, shield-shaped, and a little more 



