168 BULLETIN 100, UNITED STATES NATIONAL MUSEUM. 



the two extreme Siboga stations is still further increased by the 

 Albatross stations, and the species rises to within the littoral zone. 



AMPHIODIA DEBITA, new species. 



Plate 69, figs. 3, 4. 



Locality. — Otaru, Japan. 



Three specimens (Cat. No. 41199, U.S.N.M.). 



Description. — All the specimens are incomplete ; the dorsal surface 

 of the disk is torn off , and none of the arms is preserved for the full 

 length ; the largest is 40 mm. long. The arms must have been very 

 long. 



The mouth shields, which are of medium size, are pentagonal, 

 with a rather sharp proximal angle, limited by two straight sides; 

 these unite over very rounded angles with two other sides, which are 

 shorter than the preceding, and which converge toward the distal 

 border with which they form a rounded angle; this distal border 

 itself is narrow and almost straight. The adoral plates are small, 

 triangular, tapering inwardly, but in contact in the median inter- 

 radial line; they broaden outwardly and by a narrow process sepa- 

 rate the mouth shield from the first side arm plate. The oral plates 

 are small and rather high. The three mouth papillae are subequal, 

 thick, short, and rounded ; the two external are inserted on the oral 

 plate. The proximal is not larger than the others. 



The upper arm plates are extremely large and by themselves cover 

 almost the entire dorsal surface of the arms ; they are almost semi- 

 circular, with the proximal border very strongly convex, and the 

 distal border straight or slightly rounded; the lateral angles are 

 also rounded. They are all in contact. 



The first under arm plate is small, triangular, broader than long, 

 with the proximal base strongly notched and the distal angle 

 rounded. The following plates are rather small, pentagonal, broader 

 than long, with a very obtuse and rounded proximal angle, straight 

 lateral borders, and a distal side more or less strongly notched in the 

 middle. These plates are in contact, but, because of the notching of 

 their distal border, there remains between the successive plates a 

 more or less marked interval filled with soft tissue. 



The side arm plates, which are only slightly projecting, cany three 

 subequal conical spines with the point blunted; their length almost 

 equals that of the segment. The surface of these spines is smooth ; 

 the ventral spine is a little thicker than the two others. 



The tentacle scales are two in number ; the external, rounded and 

 inserted on the side arm plate, is of medium size; but the internal, 

 inserted on the whole length of the external border of the under arm 

 plate, is very large, elongated, and broad, with the free border convex. 



