564 
BULLETIN OF THE UNITED STATES FISH COMMISSION. 
peristome; secondaries similar, but much shorter; miliaries very slender. Primary tubercles smooth 
and imperforate, a double series on each ambulacrum, and also on each interambulacrum. On 
the ambulacra the series of primaries are separated by a double series of secondaries, while 2 or 3 
series of secondaries on the poriferous zones form transverse lines between the arcs of the pores. 
On the interambulacra there are about. 8 series of secondaries, 4 between and 2 outside of each primary 
series. Miliary tubercles occur all over the test, on both ambulacra, and interambulacra. A specimen 
with D = 30 mm., H = 17 mm., has 22 coronal plates, while one with D = 60 mm., II =27 mm., has 35. 
Buccal plates, 5 pairs, large and bearing miliaries. Pedicellarhe numerous, long stalked. Color in life 
prevailingly green; the test green or greenish white, purple or purplish white, the poriferous zones mark- 
edly lighter than the rest of the test; spines green with yellow, red, or purple cast, especially in young 
specimens; sometimes the actinal spines are bright violet, while the abactinal may be tipped with red 
or violet; pedicellaria and miliary spines whitish; tubercles white; tube feet whitish or pale violet. 
Range. — Circumpolar; southward in the western Atlantic to New Jersey ( not in shallow water south 
of Cape Cod); in the Eastern Hemisphere to Great Britain and Norway; in the North Pacific from 
Kamchatka to Puget Sound; low water to 640 fathoms. 
Remarks. — In the Woods Hole region this northern urchin is found in abundance off Sankaty Head, 
Nantucket; it is common at Crab Ledge; it has been taken at several points in Vineyard Sound, and 
it occurs in 10 to 20 fathoms off Gay Head. At Crab Ledge the specimens we took were all small, but 
off Sankaty Head a large number of good-sized individuals were secured. In spite of the fact that 
this is one of the. commonest and best known of sea-urchins, no connected account of its development 
has ever been published, although the egg, segmentation stages, pluteus, and young are all well known. 
3. Echinarachnius parma (Lamarck). Sand Dollar. (PI. 10, figs. 58-62.) 
Scutclla parma. Lamarck, 1S16. 
Echinarachnius allanticus , Gray 1825. Stimpson, 1853. 
Echinarachnius parma , Gray 1825. 
Scutclla triforia Say, 1826. 
Description. — Test greatly flattened, closely covered with minute spines, which are shortest and 
most uniform on the abactinal surface, longer at the margin, and longest in the interradial areas at the 
peristome. Ambulacra qbvious abactinally as widely open, somewhat obtuse “petals,” extending 
more than halfway to margin; actinallythe ambulacra appear as furrows, widest at peristome, and 
when more than halfway to the margin, giving off a prominent branch on each side at an angle of 
about 45°; all 3 furrows run to the margin, and the main furrow may be continued abactinally. 
Abactinal system approximately central; genital pores 4. Anal opening abactinal in very young 
specimens, marginal in adults, actinal in very large or old specimens. One of the latter gives the 
following measurements: Longitudinal diameter, 78 mm. ; transverse diameter > 78 mm. ; vertical diam- 
eter, 12 mm. ; diameter of abactinal system, 8 mm. ; length of anterior petal, 26 mm.; length of posterior 
petal, 24 mm.; length of spine at margin, 1 mm.; length of spine at peristome, 3 mm. 
In very young specimens the proportions are somewhat different; thus a specimen 8 mm. long is 
only 7 mm. broad. The greatest trail verse diameter is not always through the abactinal system, but 
may be considerably back of it, and the abactinal system may be considerably in front of the center 
of test. Thus in a specimen 12 mm. in longitudinal diameter the center of the abactinal system is only 
5 mm. from the anterior edge of the test, and the greatest tranverse diameter is through a point only 
4 mm. from the posterior edge. The relative width of the petals varies greatly; it may be anywhere 
from 37 to 50 per cent of the length. Color in life, dull brownish-red, varying from flesh-red in 
very young specimens to a deep reddish-brown in adults; interambulacra distinctly lighter than the 
ambulacra, which are quite red. When placed in fresh water or alcohol, or even when simply dried, 
the color changes to a bright, though dark green, which afterwards, in dry specimens, becomes a dull 
brown. Tbe bare, bleached tests are of course white. 
Range. — Labrador to New' Jersey; also both sides of the Pacific Ocean, from Vancouver to Japan, 
and (according to Agassiz) India, Australia, and the Red Sea. Low water to 888 fathoms. 
Remarks. — This curious species is very common on sandy bottoms in Vineyard Sound and on the 
Nantucket Shoals. The finest specimens were taken near the Great Round Shoal Lightship, Nan- 
tucket, in 12 fathoms, many of them being 3 inches or more in diameter. The sand dollar is said to 
be an important article of food for flounders and codfish. It lives more or less buried in the sand, 
moving about very slowly, chiefly by means of the spines. The development has been studied and 
partially described by Few Ices (’86), 
