OPHIURANS OF UNITED STATES NATIONAL MUSEUM. 53 



Amphiura the name of A. Jcinbergi. This term must therefore become a nomen 

 nudum. However, in order to recall its very great likeness to A. Mnbergi, which 

 is beyond dispute, I propose that the name of A. Tdnbergiensis should be given to 

 the species which is here described. 



The diameter of the disk ranges from 4.5 to 5 mm.; the arms are very long, 

 exceeding 70 mm. 



The specimens are not in a very good state of preservation; every one of them 

 has several of its arms broken and the disks also are somewhat deformed ; however, 

 the examples have quite discernible characters, and they may perfectly well be 

 described and even photographed. 



The disk is pentagonal, more or less excavated in the interradial spaces. The 

 upper face is covered with small, unequal, imbricated plates which are smaller in the 

 central region as well as in the interradial spaces and on the margin of the disk 

 and which become larger near the radial shields; there is not the slightest indication 

 of primary plates. The radial shields are elongated and triangular and their shape 

 is slightly variable; sometimes they are a little more elongated, sometimes, on the 

 contrary, they are a little widened. They display a straight and narrow radial 

 side, a very convex interradial side, and they are about three times longer than wide. 

 They are distally contiguous and separated on their whole length by more or less 

 wide spaces, occupied by several rows of plates. 



The under face is absolutely bare and its color is always dark. The genital 

 slits are fairly wide. 



The mouth shields, middle-sized, are always longer than wide. They are oval or 

 lozenge-shaped, with a rather open and rounded proximal angle, limited by two 

 convex sides; the two posterior sides are about equal in length to the foregoing 

 ones and they meet in a very obtuse angle which is sometimes truncated so as to 

 form a little rounded distal side; the very obtuse lateral angles are more or less 

 rounded, and consequently the shields are now oval, now lozenge-shaped. The 

 rather large adoral plates are triangular; the proximal side and the interradial 

 side are more or less excavated, the third side is smaller and straight. These plates 

 lie near together and generally contiguous on the interradial median line at a very 

 much rounded angle; they become wider outwardly and may even supply a narrow 

 blade which separates the mouth shield from the first lateral brachial plate. The 

 oral plates are fairly elongated. The external oral papilla is strong, thick, conical, 

 and erect, with a more or less blunt point: the internal papilla is wide and thick; 

 an intermediate papilla is located on a somewhat higher level; it is thin, conical, 

 and pointed. 



The upper brachial plates are not very large; they are, however, wider than 

 long and rather oval-shaped, with a very convex distal side and plainly rounded 

 lateral sides; they are all in contact. 



The first under brachial plate is middle-sized, trapezoidal, and somewhat 

 wider than long, with a wide and convex proximal side, and a narrower distal side 

 toward which converge the lateral sides, which are slightly excavated by the adoral 

 plates. The next plates have a general pentagonal shape, with a very obtuse 

 proximal angle which is truncated, rounded, and more or less indistinct; the 



