MUSEUM OF COMPARATIVE ZOOLOGY. 147 
set with slender stumps, having a trunk surmounted by a crown of rather long 
thorns (Fig. 263). Station 218 furnished specimens remarkable for the num- 
ber of arm-spines, with a disk of only 7 mm. and arms of 32 mm. There were 
eleven arm-spines, the uppermost being 2.3 mm. long, the lowest 1 mm., and the 
rest intermediate (P1. X. Fig. 264) ; the disk-stumps were as in Station 122, but 
stouter (Fig. 265). The great number of arm-spines in rather small individuals 
is a grave variation ; but others from the same quarter of the globe (Station 
191) were normal in this respect. A. specimen off Tristan d’Acunha had a disk 
7 mm. in diameter and the arm about 37 mm. long. The outermost mouth- 
papilla on either side was wide (Pl. X. Fig. 269), and the next two were 
longer than usual. The upper arm-spine was 3 mm. long, and feebly thorny 
for its whole length. © 
Ophiacantha cosmica appears in the entire southern hemisphere, from the 
Brazil coast, by the lone Island of Tristan d'Acunha, the antarctic zone, off 
New Guinea, and between Juan Fernandez and the South American coast, 
where it lives in 2225 fathoms, Off Brazil it is found in only 350 fathoms, Its 
extreme variations are described above, and are not very great. 
Stations 122, 350 fathoms, 12-+ specimens. Off Tristan d’Acunha, 1000 
fathoms, 2 specimens. Station 146, 1375 fathoms, 2 specimens. Station 147, 
1600 fathoms, 12-|- specimens. Station 153, 1675 fathoms, 11 specimens. 
Station 156, 1975 fathoms, 3 specimens. Station 157, 1950 fathoms, 2 speci- 
mens, and 2 young. Station 158, 1800 fathoms, 2 specimens, Station 191, 800 
fathoms, 7 specimens. Station 218, 1070 fathoms, 10 Specimens. Station 
298, 2225 fathoms, 2 specimens, Station 299, 2160 fathoms, 9 specimens. 
Ophiacantha levispina sp. nov. 
Plate X. Fig. ۰ 
Special Marks. — Disk closely beset with fine stumps bearing crowns of mi- 
nute thorns ; seven slender, not thorny arm-spines; outer side of under arm- 
plates strongly curved. 
Description of an Individual (Station 214). — Diameter of disk 6mm. Length 
of arm 36mm, Width of arm without spines 2 mm. Mouth-papille seven 
or nine to each angle, whereof the outer one on either side is brdad and scale- 
like, while the other five or seven are sharp and conical. Mouth-shields broad 
heart-shape, with the point inward ; length to breadth 1: 1.3. Side mouth- 
shields rather narrow, of nearly equal width, meeting within. Under arm- 
plates wider than long, with a slight peak within, and the outer side (especially 
little way out on arm) very strongly curved. Upper arm-plates very small, 
sunken below the ridge of side arm-plate, of a rounded fan-shape, with an angle 
inward. Side arm-plates large, meeting broadly above and below, with a spine- 
ridge which swells gradually from the plate, and does not form a steep nar- 
row crest, Disk densely beset with very fine, thorny stumps, similar to Fig. 
263, Plate X., but with a more slender trunk ; radial shields and scaling hid- 
