﻿AMPIIIURA ATRA. 127 



Araphiura atra Lutken. 



Qphkih'ph atra Stimpsox. I'roci'cd. lioston Soc. Nat. Hist., IV. p. 22.5. 1852. 

 Amphiura (Ojiliiulcplx) aim LiJTKKX. Addit. ad Hist. Oph., p. 118. 



Special Marks. — Three arm-spines ; under arm-plates narrower with- 

 out than within, their outer side re-enteringly curved ; mouth-i^apilloe 

 making a connected line ; innermost pair running upwards to the teeth. 



Descripiion of a Specimen. — Diameter of disk, 9.5™""' ; from outer 

 side of mouth-shield to outer corner of opposite mouth-slit, 3.6™™' ; 

 width of arm without spines, 2'"°'- ; length of arm about 95"""- ; dis- 

 tance from outer side of mouth-shield to inner points of niouth-papillo?, 

 to that between outer corners of mouth-slits, 1.6 : 1.6. Mouth-papillaj 

 wide, somewhat angular, applied end to end, so as to form a connected 

 Ime ; innermost pair extending upwards towards the teeth, and thus 

 partly holding the place of tooth-papillae ; usually six, sometimes eiglit, 

 to each angle of the mouth. Teeth nine ; lowest one small, irregular, 

 often broken in two or three pieces ; the rest squarish, flattened, very 

 regular, mcreasing a little in size towards the upper ones. Mouth- 

 shields small, diamond-shape, longer than broad ; length to breadth, 1 :.6 ; 

 madreporic shield larger and swollen. Side mouth-shields comparatively 

 large, meeting within, broader without than Avithin, and with a slight 

 curve like an S. Under arm-plates broader than long, broader within 

 than without ; inner and lateral sides neai'ly straight, outer side re- 

 enteringly curved, corners rounded ; length to breadth (seventh plate), 

 .5 : .8 ; the plates are in contact only at the base of the arm ; about the 

 twelfth plate they begin to be separated by the side arm-plates, and 

 begin also to have a slight peak on their inner side, which is the point 

 of juncture of two slightly curved inner laterals ; the first plate is quite 

 rudimentary. Side arm-plates rather feeble, long, encroaching above 

 and below, having a very small ridge for spines. Upper arm-plates 

 much broader than long, pointed oval, with outer side nearly straight, 

 and inner sides curved ; separated from each other except on the mid- 

 dle line ; length to breadth (tenth plate), .6 : 1.7. Disk with closely 

 overlapping scales, about 36 to a square mm. ; below finer ; near radial 

 shields larger ; from near the outside corner of the radial shields runs a 

 single straight row of larger scales, passing diagonally over the edge 

 of the disk. Radial shields rather large, irregular oval, with a point 

 within, united without, within separated by a group of scales ; length to 

 breadth, 2 : .9. Arm-spines short, round, tapering, sharp ; lengths of two 

 lower ones to that of under arm-plate, near base of arm, .9, .9 : .5 ; upper 

 one somewhat shorter. Tentacle-scales two, broad, short, erect, with a 



