OPHIUKANS OF UNITED STATES NATIONAL MUSEUM. 51 



The diameter of the disk is 7 mm.; the arms are broken off near the base. 



This Ophiura was labeled Amphiura flexuosa by H. L. Clark, but it is undoubt- 

 edly incorrect; in fact, the individual differs from A. flexuosa which I have 

 described above to such an extent that it is impossible to refer it to that species; 

 besides, it comes nearer A. latispina, but also differs from it, and I consider it to 

 represent a new species. 



The disk is pentagonal, excavated in the interradial spaces. The upper face 

 is covered with middle-size plates, which are fairly uniform and regular, imbri- 

 cated, with no indication of primary plates. They only become a little smaller 

 toward the outline in the middle of the interradial spaces. The radial shields are 

 narrow and rather elongated, three or three-and-a-half times longer than wide, 

 with a very pointed proximal angle; they are hardly divergent and separated on 

 their whole length by a set of plates; their length is inferior to half the radius of 

 the disk. The upper plates stop in a very sharp manner at the periphery of the 

 disk, when they reach the edge of the under face ; this face remains bare or provided 

 only with a few very thin scales, which are insulated or united into small groups, 

 but by no means form a regular covering. The genital slits are narrow. 



The mouth shields are fairly large, elongated, much longer than broad, and 

 lozenge-shaped, with a truncated and rounded distal angle. The adoral plates 

 are triangular, hardly in contact by their internal angle on the median line. The 

 oral plates are short and thick. The external mouth papilla is erect, somewhat 

 spiniform although short, and slightly flattened with a blunt point; the internal 

 papilla is conical, rather thick, and of middling size. Another papilla, which is 

 almost identical with the external, one, but somewhat thicker at its basis, is found 

 between the two preceding ones on a higher level. 



The arms are elongated and fairly thin. The upper brachial plates are very 

 large, much broader than long and cover a great part of the upper face of the arms. 

 The first two or three are quadrangular, with a narrow proximal edge, a very wide 

 and strongly convex distal edge, and diverging sides. The following plates take 

 the shape of a biconvex lens, with the two anterior and posterior edges united by 

 rounded angles. 



The first under brachial plate is trapezoidal, almost as broad as long, with a 

 narrow and slightly convex* distal edge. The following ones are pentagonal, a little 

 wider than long, with a very obtuse and rounded proximal angle and a distal edge 

 which is slightly excavated hi its middle. They are all contiguous. 



The lateral plates, little protruding, carry five spines each. The first ventral 

 spine is conical with a blunt point, and its total length is equal or slightly superior 

 to that of the article. The second spine, which is a little larger, first has the same 

 shape as the preceding one, then, beyond the disk, its extremity gets elongated 

 and developed into a hyaline hook, which is bent and strongly marked. The 

 third spine, which is shorter than the second and as long as the first, also tends to 

 form a hook at its end, but this hook is less developed and less bent than the fore- 

 going one. The fourth spine is still shorter, and the fifth, which is but little 

 developed, hardly reaches half the article; the last two spines are cylindrical and 

 not very thick. 



There are two tentacular scales rather short, subequal and at a right angle. 



