168 



BULLETIN 75, UNITED STATES NATIONAL MUSEUM, 



Localities. ^Albatross station 5053, Siiruga Gulf, lat. 34° 49' 20" 

 N.; long. 138° 40' 15" E., 503 fathoms, green mud, bottom tempera- 

 tm-e 34.9°, 1 specimen; station 5054, Suruga Gulf, lat. 34° 52' 45" 

 N.; long. 138° 42' 20" E., 282 fathoms, green mud, broken shells, 

 foraminifera, bottom temperature 45.3°, 2 specimens, without disks; 

 station 5088, Sagami Bay, lat. 35° 11' 25" N.; long. 139° 28' 20" E., 

 369 to 405 fathoms, green mud, bottom temperature 41.8°, 1 speci- 

 men. Bathymetrical range, 282 to 503 fathoms. Temperature 

 range, 45.3° to 34.9°. Four specimens. 



Type.— Cat. No. 25587, U.S.N.M., from station 5053. 



The extremely slender arms and tlie characteristic mouth parts, 

 taken in connection with tlie radial shields, three arm spines and two 

 tentacle scales, make this an easy species to recognize. As the disks 

 are wanting in the specimens from station 5054, it is, of course, possi- 

 ble that their identification as rhadinobracMus is incorrect. 



Fig. 74.— Amphioplus rhadinobrachius. X 8. a, from above; h, from below; c, side \iew of 



THREE ARM JOINTS NEAR DISK. 



AMPHIOPLUS ACANTHINUS, new species." 



Disk 14 mm. in diameter; arms about 140 mm. long. Disk some- 

 what decagonal (the decagon with somewhat convex sides), lightly 

 notched radially, and deeply so interradially; covered with a close 

 coat of very numerous scales, some of wdiich bear slender acute spines 

 one-half millimeter long; these spines are set into little pits, so that 

 when they are rubbed off their former position is clearly indicated. 

 Radial shields small, divergent, but in contact distally. Upper arm 

 plates tetragonal or pentagonal with more or less rounded corners, 

 twice as wide as long or more, broadly in contact basally but barely 

 touching on terminal part of arm. Interbrachial spaces below covered 

 by nuicli finer scales than the disk, and without s})ines. Oral shields, 

 oval or elliptical, much longer than wide. Adoral plates large and 

 triangular, hardly meeting within. Oral papillae four or five on a side, 

 the one near apex of jaw largest. Genital slits very large; genital scales 

 inconspicuous orally, but often noticeable from above just distal to 

 the radial shields, and frequently bearing there a little outgrowth simi- 



"■ AKoudivof, signifying thorny, in reference to the numerous disk spines. 



