126 BULLETIN 100, UNITED STATES NATIONAL MUSEUM 
Description—The largest of the three specimens is 40 mm. long, 
28 mm. broad, and 17 mm. high, the others a little smaller. The test 
is very elongate and narrow; the greatest breadth is at the middle 
of the test, from where it narrows gently toward both ends. The 
greatest height is behind the posterior petals; from there the test 
slopes very gradually toward the posterior end, the periproct being 
completely visible when the test is viewed from above. The frontal 
depression is moderate; oral side flat, but the narrow sternum rising 
into a conspicuous knob at its posterior end. The peristome is placed 
rather far from the anterior edge. The labrum reaches posteriorly 
to the middle of the second adjoining ambulacral plates. Five am- 
bulacral plates reach within the subanal fasciole, the first of them 
being the sixth. The petals are rather short but relatively broad 
and only slightly sunken; the posterior petals are confluent proxi- 
mally, but the pores of the inner (posterior) series are rudimentary 
only in about the proximal half of the petal. The tube feet of the 
frontal ambulacrum are long and reddish, with an unlobed sucking 
disk. The apical system is central. The periproct is produced at 
its upper end. 
It is a noteworthy feature that the spines within the subanal 
fasciole form a pair of conspicuous tufts. The peripetalous fasciole 
bends only slightly inward between the petals. The subanal fasciole 
is almost circular, nearly as high as it is broad; the anal branches 
are well developed. 
The globiferous pedicellariae have rather slender valves, terminat- 
ing in two long divergent teeth. The tridentate pedicellariae have 
very simple, narrow valves. Rostrate pedicellariae not peculiar; 
ophicephalous pedicellariae appear to be lacking. 
Color of test and spines whitish, but the subanal fasciole somewhat 
darker and thus quite conspicuous. 
Remarks—The strongly sloping posterior end of the test, the 
posterior prolongation of the labrum, reaching to the middle of the 
second adjoining ambulacral plates, and the conspicuous tufts formed 
by the spines within the subanal fasciole distinguish this species 
very markedly from all the other species of Brissopsis known from 
the Indo-West Pacific. 
BRISSOPSIS OLDHAMI Alcock 
Brissopsis oldhami Axcock, Journ. Asiatic Soc. Bengal, vol. 62, p. 174, pl. 8, 
figs 7. 8, 1893.—A. Agassiz and H. L. CiarKk, Bull. Mus. Comp. Zool., vol. 
50, p. 256, 1907; vol. 51, p. 186, 1907.—KorHter, Echinoderma of the Indian 
Museum, Echinoidea, pt. 1, Spatangidés, p. 218, pl. 14, figs. 1-3, 8, 9, 15; 
pl. 15, fig. 12; pl. 20, figs. 28-43, 1914. 
Localities —Station 5468, Atalayan Island (lat. 13°40’ N., long. 
123°40’ E.) ; 1,041 meters; June 18, 1909. Two specimens, the larger 
