174 Proceedings of the Biological Society of Washington. 



The side mouth shields are about four times as long as broad, with 

 parallel sides, in apposition inwardly. 



The mouth frames are similar to, and not much larger than, the side 

 mouth shields. 



The mouth papilte are five in number, the first two relatively long, and 

 conical, the third of about the same basal length, but lower with a 

 rounded outer border, the fourth of the same height as the third but 

 twice as long with a straight outer margin, the fifth similar but nearly 

 three times as long as the fourth, with a straight outer margin. 



The first arm tentacle lies in a tube consisting of four rounded tentacle 

 scales inwardly, and three outwardly, the two tentacle slits in each inter- 

 radial area being parallel and not connected with the mouth slits. 



The first upper arm plate is small, transversely oval, from two to three 

 times as broad as long; the second is much larger, reaching almost en- 

 tirely across the arm as viewed dorsally, twice as broad as long, the 

 proximal and distal borders strongly curved and parallel, the lateral 

 edges converging slightly ; the following upper arm plates become rapidly 

 narrower, the fifth being an elongate triangle, twice as long as the distal 

 width, the apex resting on the distal border of the preceding; beyond 

 the fifth the upper arm plates, becoming progressively smaller, are more 

 and more widely separated from each other by the apposition of the side 

 arm plates, on the outer portion of the arm being small and inconspic- 

 uous quadrilateral plates with the proximal angle more produced than 

 the distal, inserted between the distal inner borders of the apposed side 

 arm plates. 



The arm spines are three, extremely short, well spaced, the uppermost 

 slightly further from the middle than the latter is from the lowest. 



The first under arm plate is triangular with very broadly rounded 

 angles and a somewhat abrupt rounded extension occupying the central 

 quarter of the distal edge; the second is slightly broader than long, 

 fan-shaped, with a truncated proximal angle, with a strongly and evenly 

 convex distal border and strongly concave sides forming the inner bor- 

 ders of two broad diverging slits which accommodate the tentacles, 

 protected by three tentacle scales; the third is more broadly fan-shaped 

 than the preceding, and is excluded from contact with it by the apposi- 

 tion of the side arm plates for a distance of half its length; the following 

 under arm plates rapidly become smaller and relatively broader. 



Type.— Cat. No. 38,670 U. S. N. M., from "Albatross" Station 2792, 

 off the coast of Ecuador, in 401 fathoms. 



