MUSEUM OF COMPARATIVE ZOOLOGY. 37 



fine, crowded, irregular, thin scales, of the smallest of which there are about 

 5 in the length of 1 mm. Those near the radial shields are much larger ; 

 and there may be also obscurely distinguished six round primary plates, widely 

 separated by the fine scaling. The disk margin is beset with minute, sharp, 

 peg-like spines. Radial shields long and narrow, touching without, separated 

 within by a narrow wedge of about three scales ; length to breadth 1.3 : .4. 

 Five short, thick, blunt, flattened arm-spines, of which the uppermost is the 

 stoutest, but not longer than the rest. One oval tentacle-scale. Color in alco- 

 hol, above, olive green, mottled and banded with lighter ; below, yellowish 

 brown, with under arm-plates and arm-spines marked with orange. 

 Port Jackson, Australia, 30-35 fathoms, 1 specimen. 



Ophiactis flexuosa sp. nov. 



Plate XIII. Figs. 34? -349. 



Special Marks. — Disk-scales distinct and naked, without spines. Three 

 stout, blunt, tapering, cylindrical arm-spines. One large flat mouth-papilla on 

 each side. Teeth lobed. Five arms. 



Description of an Individual (Station 171). — Diameter of disk 7 mm. Length 

 of arm about 35 mm. Width of arm near disk 2.3 mm. Each side of the 

 short, narrow mouth -angle is occupied by a single very large, wide, flat papilla, 

 while a third, standing under and resembling the teeth, is at the apex, and has 

 a rounded figure, with a decided peak or little lobe within. Mouth-shield 

 somewhat broader than long, of a rounded diamond-shape. Side mouth-shields 

 rather broad, wider without than within where they meet. First under arm- 

 plate small, and wider within than without ; those beyond are narrow com- 

 pared with the width of the arm, much rounded, of* a short transverse oval 

 shape, with the inner side somewhat angular. Side arm-plates very wide, 

 meeting neither above nor below, and having but a feeble lateral projection. 

 Upper arm-plates broad and short, two and a half times as wide as long, of an 

 elongated transverse diamond-form, sometimes with outer side so straight as 

 nearly to be triangular. Disk without spines, and covered above with coarse, 

 rounded, thick, overlapping scales, of which there are four or five radiating rows 

 in the narrowest part of each interbrachial space. Below, the scales of the in- 

 terbrachial space are much finer (4 or 5 in the length of 1 mm.), and regularly 

 imbricated. Three short, stout, cylindrical, scarcely tapering arm-spines of 

 nearly equal length, and about as long as one and a half joints ; the upper 

 spine stoutest. One large oval tentacle-scale. Color in alcohol, pale brown. 



Station 171, 600 fathoms, 2 specimens. Station 142, 150 fathoms, 10 speci- 

 mens, young ? 



The ten specimens from Station 142, 150 fathoms, may be the young of this 

 species. They have six arms, while 0. Jlexuosa has but five, and are scarcely to 

 be distinguished from O. plana ; and the question arises whether O. plana be 

 not a young animal. The so-called adult of 0. Mulleri has five arms, and the 

 young six. 



