46 BULLETIN 84, UNITED STATES NATIONAL MUSEUM. 



extremity. H. L. Clark has reported A.fiexuosa at Porto Rico in a depth ranging 

 between 162 and 171 fathoms, but he points out that the second under spine of his 

 specimen has its extremity bent. We will see further that Ljungman's type does 

 not offer this character. 



I have had in hand a certain number of Amphiuridse of the West Indies, 

 either from the Albatross Expeditions or from Messrs. Kiikenthal and Hartmeyer's 

 voyage, some of which have the imder face of the disk bare, while the others have 

 it covered with scales; in some of them also the spines are variably bihamuled, 

 and for certain specimens, a comparison with A.fiexuosa was indispensable. Before 

 anything else, I thought it necessary to determine accurately the characters of 

 this species and to study its type as minutely as possible; thanks to Professor 

 Th^el's kindness I was able to secm^e the loan of this type, and I think it useful 

 to give here a description with some illustrations. Unfortunately, the specimen is 

 not in a perfect state of preservation and the disk is incomplete, but the characters 

 can nevertheless be perfectly well discerned. 



Ljungman says that the diameter of the disk is about 7 mm., but it seems to me 

 to scarcely reach that figure; the longest arm is preserved to a length of over 45 mm. 



The disk is rounded, very deeply excavated in the interradial spaces. The 

 upper face is covered with fairly large imbricated plates which are subequal, and 

 become smaller in the middle of the interradial spaces and a little larger in the 

 vicinity of the radial shields. The latter are triangular, very long and narrow, 

 with a narrow basis and a very acute proximal angle; they are fairly divergent, 

 contiguous distally on about a third of their length and separated proximally by 

 several rows of plates; as indicated by Ljimgman, their length is equal to half the 

 radius of the disk. 



The upper plates of the disk extend over to the under face and they form 

 around that face a narrow peripheric border which is very sharply limited mwardly, 

 but all the rest of the imder face is absolutely devoid of plates; it displays only a 

 thin and transparent tegument, slightly plaited and dark-colored. The genital plates 

 are elongated and narrow; the genital slits are very conspicuous and rather wide. 



The mouth shields, almost as long as wide, are rather small and their shape 

 may be compared to a triangle with a strongly convex proximal basis, excavated 

 lateral borders which join, by rounded angles, a straight and naiTow distal side 

 which represents the tnmcated apex of the triangle. It might also be said that 

 these shields have a pentagonal shape with a very obtuse and romided proximal 

 angle, limited by convex sides, slightly excavated lateral edges, and a small distal 

 edge. The adoral plates are triangular, with an almost straight distal side, and 

 two other deeply excavated sides; these plates are limited to the sides of the mouth 

 shield, and their rounded internal angles are widely separated on the interradial 

 median Ime; distally, they become wider and form a narrow blade which separates 

 the mouth shield from the first lateral brachial plate. The oral plates are high 

 and rather narrow. The external oral papilla is conical, spmiform, fairly strong, 

 and ends in an obtuse pouit; it is obliquely erect; the internal papilla is thick and 

 oval ; between these two papillae there is, on a higher level, an mtermediate papilla 

 which is directed horizontally and is of conical shape, but it is thinner and more 

 pointed than the external one. 



