MUSEUM OF COMPARATIVE ZOOLOGY. 147 



set with slender stumps, having a trunk surmounted by a crowTi 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 (PI. 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 (PI. 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 -f 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. 377. 



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 6 mm. Length 

 of arm 36 mm. Width of arm without spines 2 mm. Mouth-papillsc seven 

 or nine to each angle, whereof the outer one on either side is broad 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 sjtine- 

 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- 



