404 PROCEEDINGS OF THE NATIONAL MUSEUM. VOL. XXXIV. 
Genus AMPHIURA Forbes. 
AMPHIURA SANCTACRUCIS, new species. 
‘Plate XL. 
Description.—Disk attaining a diameter of 13 mm., delicate, cov- 
ered with small naked, overlapping scales. Arms five, long, slender, 
even or tapering very slightly and more or less flattened. Arm 
spines moderately short and sharp pointed, approximately equal in 
length to the width of the dorsal median plates. Upper arm plates 
simple, breadth about 14 length; lower arm plates deeply grooved 
in the median line. 
Disk pentagonal in outline, the arms passing out from the sides 
rather than from the angles, this being due to the spreading of the 
disk upon compression by the containing fine clayey sediments; whole 
dorsal surface of disk covered with overlapping scales, which, in the 
cast serving as the type, are minutely shallowly punctuate corre- 
sponding to numerous microscopic protuberances in the original ani- 
mal. Radial shields moderately large, of a short, pear-seed shape, 
pointed within, outer edge sharply rounded, inner edges nearly 
straight and separated by 5 prominently overlapping scales (the 
continuation of the upper arm scales, but shorter than the latter), 
which narrow rapidly toward the points of the shields. Between 
the radial shields of adjacent arms are about 7 rows of small over-— 
lapping plates, the middle row apparently much larger than the 
others. The specimen exhibiting the ventral side is so much crushed 
that its characteristics are unrecognizable. Upper arm plates simple, 
small, breadth about 14 length, shghtly narrowed within, broader | 
without, straight front, back and sides. Side plates small, triangular, 
with sharp cornered, beveled edges. Under arm plates quite similar 
to upper, except deeply medially longitudinally grooved. Spines 
at least 4 to a segment; about 14 times length of upper arm plates, 
rounded, sharp. | 
Dimensions.—Specimen exhibiting dorsal surface; diameter of 
disk 13 mm.; arms at least 25 mm. long, and probably several times 
this amount; width near disk 2 mm., upper arm plates 0.7 to 0.8 
mm. long. 
Specimen exhibiting ventral surface: diameter of disk 6.5 mm. ; 
arm at least 20 mm. long and probably at least twice this length 
judging by taper. 
Notes.—The two specimens upon which this species is founded 
are beautifully preserved molds, the larger one, which is taken as 
the type, showing the dorsal surface, the smaller one the ventral. 
As would be expected, the surfaces of the disks are considerably 
crushed and distorted, but enough characteristics are visible to admit 
