MUSEUM OF COMPARATIVE ZOOLOGY, 103 
A young O. sericeum (disk 7.5 mm.) was very like a still smaller O. gracilis (disk 
6.8 mm.), which had the arm-comb less marked ; but other specimens had it 
just the same. A number of specimens marked as O. sericeum (young) and 
O. gracilis showed variations in number of papilla along the genital openings, 
coarseness of disk-scales, more or less pointed tentacle-scales, and length of 
spines ; but all these variations seem common to both, in a greater or less de- 
gree, The two specimens of the “Challenger” Expedition showed no valid 
difference with the half-grown 0. sericeum, except in absence of papilla along 
the genital opening ; but two specimens from George’s Bank, off Massachusetts, 
were in this respect intermediate, and had hardly any papilla in that region. 
Off Marion Island, 50 — 75 fathoms, 2 specimens. 
Ophiocten hastatum sp. nov. 
Plate V. Figs. 133, 134, 
Special Marks. — Disk with minute thin scales, among which appear well- 
marked primary plates. Three tapering arm-spines, the upper much the 
longest and largest. One minute tentacle-scale. 
Description of an Individual (Station 146.) — Diameter of disk 9 mm. 
Width of arm close to disk 2 mm. Four or five short, squarish, close-set 
mouth-papillo on each side, with one much larger at apex of jaw, having two 
small bead-like ones at its base. Mouth-shield rounded pentagonal, having 
a broad angle within. Side mouth-shields long and narrow, of about equal 
width, nearly or quite meeting within. First under arm-plate larger than any 
of the others, four-sided, with inner side much narrower than the outer, which 
‘is slightly rounded ; the remainder of the under arm-plates are much wider 
than long, and nearly semicircular, with a slight peak inward, and outer side 
deeply curved. Side arm-plates somewhat swollen and flaring outward, meet- 
ing broadly below ; separated above by the upper arm-plates, which are some- 
what arched, with the inner side narrower than the outer, which is curved. 
Disk round, smooth, and flat, covered, above and below, with minute thin scales ; 
in the centre are several rounded. primary plates, and one of nearly equal size 
in each interbrachial space. Radial shields pear-seed shape, with inner angle 
blunt, and outer corners rounded ; separated their entire length by fine over- 
lapping scales. Genital scales hidden, except their tips, outside the radial 
shields, which bear an arm-comb of a few minute papille, as does sometimes 
the first upper arm-plate. Three slender, cylindrical, tapering, pointed arm- 
spines, the upper one being much longer and larger than the two lower ; lengths 
to that of an arm-joint 3.4, 1,.8: 1. Tentacle-scales minute and rounded ; 
there are two or three to. each of the second mouth-tentacles ; usually one on 
the outside of the basal pores, and one on the inside of the pores farther out 
on the arm. Color in alcohol, disk nearly white ; arms above pale gray. 
Station 78, 1000 fathoms, 2 specimens. Station 146, 1375 fathoms, 12 + 
specimens. Station 168, 1100 fathoms, 12 + specimens. 
