orHioMusiuM. 115 



meeting above and below. Upper arm-plates narrower tban the 

 arm, much longer tban wide, bounded on all sides by gentle curves. 

 Disc covered with thin, irregular, overlapping scales, and having in 

 tbe centre a group of much larger rounded primary plates, 1 mm. in 

 diameter. Below the scaling is similar but finer. Radial shields 

 narrow oblong, or egg-shaped, small, separated by a narrow wedge 

 of fine scales ; length to breadth, 2:1. Genital openings large and 

 long, extending from mouth-shield to margin of disc. Three smooth, 

 slender, tapering arm-spines, whereof the uppermost may be as 

 long as two joints. Lengths, to that of an under arm-plate, 

 2-5, 1*2, 1-2, : 1. One oval tentacle- scale of moderate size. 



" Colour in alcohol, nearly white. 



" ' Porcupine ' Expedition, 1869, Station 42, south-west of Ireland, 

 862 fathoms, water 4°-3 Cent. ; 1 specimen." 



I have never seen this species, of which I quote Mr. Lyman's 

 original description. 



AMPHIURID^E {see p. 25). 



1. OPHIOMUSIUM. 



Ophiouiusium, Lyman, Bull. M. C. Z. i. (1869 ) p. 322 ; id. Chall. Rep. 

 Oph. (1882) p. 83. 



No tooth-papilke ; teeth ; mouth -papillae confluent. Very large 

 radial shields with intermediate plates form a stout covering to the 

 disk ; upper and lower arm-plates reduced or absent ; side-plates 

 meet above and below ; arm-spines very small. Tentacle-pores 

 confined to area of disk. 



1. Ophiomusium lymani. 



Ophiomusium lymani, Thorns. Depths of the Sea, (1873) p. 174, 

 figs. S2&33; Lyman, Chall. Hep. Oph. (1882) p. 90; Hoyle, Proc. 

 Roy. Phys. Soc. Ed. viii. (1885) p. 151. 



Inner half of the disk occupied by five or six circlets of small 

 irregular plates set round a single central and circular plate. 

 Eadial shields irregularly triangular, large, each member of a pair 

 separated from its fellow, and from the adjoining pair by bands of 

 about equal length formed by a few well-sized but not constantly 

 regular plates. Five teeth ; there are signs of the mouth-papillae, 

 when separate, having been seven in number. Mouth-plate shield- 

 shaped, much wider behind them near the mouth, where it is pointed ; 

 side-shields united in front of the mouth, longer than broad, irre- 

 gularly oblong. Bursal slits rather short; the free part of the 

 adjoining scale with a sharp edge. Two large, irregularly quadrate 

 plates outside the mouth-shield. The lower marginal plates swollen, 

 few in number. Under arm-plates and single tentacle-scales on 

 the first two arm-joints only. Upper arm-plates convex forwards, 

 small, getting smaller, and disappearing altogether at about the 



i2 



