REPORT OF THE ECHINOIDEA—MORTENSEN 133 
Description.—The holotype is 22 mm. long, 20 mm. broad, and 8 mm. 
high; the specimen from station 5257 is of the same size; the other 
specimens are smaller; the one from station 5104, the smallest, is 13 
mm. long, 11.5 mm. broad, and 6 mm. high. 
From Maretia planulata of corresponding sizes the present species 
differs in being broader and also slightly higher; but particularly it 
differs from planulata in having the depression of the frontal edge of 
the test broader and deeper, the test being distinctly heart-shaped. On 
the oral side the anterior ambulacrum is conspicuously sunken, which 
it is not in planulata. The petals are a little shorter than those of 
planulata of corresponding sizes. The peristome is rounded pentago- 
nal; the labrum, which does not form a prominent lip, reaches poster- 
iorly to the end of the third adjoining ambulacral plates, as in planu- 
lata. The periproct is only about as long as broad and is nearly round 
in outline, whereas in planulata it is much longer than broad, pointed 
at both ends. The subanal fasciole is well developed; only two tube 
feet to each side within the fasciole. The long aboral spines are about 
equally long and numerous in both species, but somewhat slenderer in 
cordata. A very conspicuous difference between the two species is 
found in the basal widening of the spines of the lateral interambulacra ; 
it is much shorter in cordata than in planulata. The pedicellariae are 
not markedly different from those of planulata, but I have found only 
a very small form of tridentate pedicellariae, whereas the rostrate 
grow to quite a fair size. The color is whitish, the type specimen with a 
faint tinge of reddish on the spines at the posterior end. 
Probably none of the specimens at hand are adult; but genital pores 
are present already in the youngest of them. 
EURYPATAGUS, new genus 
Test low, arched: oral side flat, but sunken at the peristome. Out- 
line elliptical, no groove or depression in the frontal edge; the poste- 
rior end slightly produced. Paired ambulacra distinctly petaloid, 
continuing to the edge of the test, open distally; frontal ambulacrum 
very narrow, the pores very small. The phyllodes of the anterior 
paired ambulacra very conspicuous, with 12-14 pores (tube feet) in 
each series, each accompanied by a sphaeridium. Peristome broad, 
pentagonal, rather far from the anterior edge. Labrum well devel- 
oped, with a narrow posterior prolongation ending off the middle of 
plates No. 4 of the adjoining ambulacral series. Plastron very small, 
entirely naked, or at most with a very few tubercles (spines) at the 
posterior end. The 3 or 4 ambulacral plates adjoining the episternal 
plates adproctally prolonged, indicating the presence of a subanal 
fasciole in the young specimens; but there is no trace of such fasciole 
in the adults. No internal or peripetalous (or marginal) fasciole. 
Periproct placed vertically on the posterior end of the test, somewhat 
