Verrill, JVotcs on Radlata. 263 



The second, tliird and fourth plates have a somewhat different form, 

 the outer edge being broader than the inner, and tlie sides concave. 

 Upper arm-phites broad and somewhat irregular-oval, about twice as 

 broad as long, the inner edge much more strongly arched than the 

 outer, which, on some of the plates near the base of the arms, is 

 slightly concave in the middle. Side-plates encroaching but little 

 above and scarcely any below, except toward the ends of the arms. 

 Arm-spines three, nearly equal, a little thickened near the base, round, 

 slender, tapering, but not sharp. Tentacle- scale oblong, flattened, 

 rounded at the end, hardly twice as long as wide, standing free from 

 the sides of the lower plates, except at the second and third from the 

 base, where they are shorter and in close contact with the lower arm- 

 plates. 



Disk, above, covered with unequal, rounded, overlapping scales ; a 

 larger, round, central, primary plate is surrounded by smaller ones, 

 and then by five primary ones about as large as the central one, each 

 of which is surrounded by a few smaller scales ; from these five a row 

 of primary plates, bordered on each side by smaller imbricated scales, 

 radiates to each interbrachial margin. Radial shields pear-seed-shaped, 

 with the point inward, the outer side strongly arched, the inner sides 

 in contact at the outer end, separated inwardly by three scales, of 

 which the most exterior is elongated and narrow and the most interior 

 broad, rounded, the intermediate one somewhat triangular. Between 

 each radial shield and the base of the arm there are two or three 

 scales and a small papilla-like spine, not one-fourth as long as the 

 arm-spines. Lower side of disk destitute of scales, but bearing minute, 

 scattered granules. 



Color, in alcohol, light greenish gray above, darker and more dis- 

 tinctly greenish toward the ends of the arms, which are banded with 

 whitish ; radial shields and primary disk-plates green ; beneath white, 

 chewing apparatus yellowish. 



An average specimen has the arms 1*38 inches long with the disk 

 •IV in diameter. One of the larger is "2 in diameter of disk; the 

 arms, though broken at the ends, 1*8. The largest is '22 in diameter 

 of disk. 



Panama, — F. H. Bradley. Eight specimens, 4 fathoms, muddy 

 bottom. 



This species very closely resembles H. cordifera of South Carolina, 

 which has the habit of living buried in mud at low-water mark and 

 thrusting out of its burrow one of its long slender anus. It difiers, 

 however, in the form of the mouth-shields and lower arm plates, as 

 well as in several other particulars. 



Trans. Connecticut Acad., Vol. I. 34 March, 1867. 



