170 BULLETIN 75, UNITED STATES NATIONAL MUSEUM. 



largely in contact." One of the specimens from station 3695 affords 

 such a remarkably fine illustration of arm and disk regeneration after 

 breaking and shedding, that it has seemed wise to show it (fig. 75d). 

 The limits of the original disk are plainly shown on the bases of the 

 four large arms, while the fifth arm is regenerating from a single basal 

 joint The disk scales are surprisingly small, and the radial shields 

 are very inconspicuous. The disk spines are represented by minute 

 knobs. Two of the four large arms are regenerating from basal 

 stumps. 



AMPHIOPLUS HEXACANTHUS, new species." 



Disk lacking. Upper arm plates broadly hexagonal, with rounded 

 corners, twice as wide as long. Arm spines six, about equal to joint; 

 middle ones shortest and one or more terminated by a minute, 

 glassy crossbar. Oral shields oval, longer than wide. Adoral plates 

 large, meeting broadly within. Oral papillae, four on a side, sub- 

 equal or apical one largest. Under arm plates squarish or slightly 

 pentagonal, rather wider than long. Tentacle scales, two. 



Localities. Albatross station 3165, off California, lat. 37 59' 45" 

 N.; long. 123 8' 35" W., 50 fathoms, green mud, bottom tempera- 

 ture 49, 6 specimens; station 5094, Uraga Strait, lat. 35 4' 42" N.; 

 long. 139 38' 20" E., 88 fathoms, black sand, broken shells, bottom 

 temperature 54.8, several arms. 



Type.C&t. No. 25583, U.S.N.M., from station 3165. 



The absence of any disks makes it impossible to describe this form 

 with sufficient detail to be satisfactory, but at the same time, since I 

 do not know of any species to which these mutilated individuals can 

 be assigned, it is only fair that they should be named, and such 

 distinctive features as they have, be described. It is possible that 

 they belong in AmpJiilimna rather than in Amphioplus. 



AMPHIOPLUS MEGAPOMUS, new species.6 



Disk lacking. Upper arm plates tetragonal, two or three times as 

 wide as long, with distal side much longer than proximal and lateral 

 corners rounded, broadly in contact. Arm spines three, longer than 

 joint, middle one longer and thicker at base than the others. Oral 

 shields diamond-shaped, with rounded corners and somewhat con- 

 cave sides, much longer than wide. Adoral plates moderate, almost 

 triangular. Oral papillas four on a side, the apical ones small and 

 widely separated from each other, the other three large, and nearly 

 closing the mouth slit. Under arm plates broadly pentagonal, much 



a "E, signifying six, and aKavOa, signifying spine, in reference to the number of 

 arm spines. 



bMej-ae, signifying big, and xaJjia, signifying lid, in reference to the large lid-like 

 tentacle scales. 



