REPORT ON THE OPHIUROIDEA. 95 



occupied by six primary plates, one pentagonal, surrounded by five rudely hexagonal. 

 The radial shields are pear-seed shape, and large, having a blunt angle inward, and 

 outer edge much rounded ; they touch only at their middle point, and are separated 

 within and without by a small triangular scale. The interbrachial space below is covered 

 by the large marginal plate, already mentioned, and the stout genital scales. Tentacle 

 scales minute, circular, situated at the inner corners of the second and third plates. 

 Two very small, short, and blunt arm spines. Colour in alcohol, white. 



Station 219.— March 10, 1875; lat. 1° 50' S., long. 146° 42' E. ; 150 fathoms; 

 mud. 



Ophiomusium scalare, Lym. (PL I. figs. 4-6). 



Ophiomusium scalare, Lym., Bull. Mus. Comp. Zool., vol. v., part 7, p. 117, pL i. figs. 1-3, 

 1878. 



Most of the lower interbrachial space, outside the mouth shield, is occupied by broad 

 genital scales and a great central plate. No under arm plates beyond the third. Three 

 short, stout, well-defined arm spines. Disk plates thick, separated by narrow grooves, 

 and arranged above like steps. Side arm plates flaring a little outward. 



(Type specimen from Station 171.) Diameter of disk 5 mm. Width of arm without 

 spines 1 mm. Length of arm about 10 mm. Mouth papillae three on each side, and 

 one at angle of jaw, closely soldered together, forming high continuous ridges, radiating 

 from the mouth. Mouth shields five sided, having a long acute angle within, and the 

 outer side straight ; length to breadth 1:1. Side mouth shields long, narrow, meeting 

 within ; broader without than within, where they join the first side arm plate ; length 

 1 mm. Genital scales large semicircular, somewhat swollen. Under arm plates minute, 

 three in number ; the first one semicircular, wedged between the side mouth shields ; 

 second and third longer than wide, with acute angle inward, lateral sides straight, and 

 outer side slightly curved. Tentacle scales round, very small, situated near inner angle 

 of the under arm plate. Side arm plates thick, swollen, covering almost the entire arm 

 beyond the disk. Upper arm plates minute, diamond-shaped. Under surface of disk 

 covered, in the interbrachial spaces, by genital scales, and three large swollen semicircular 

 plates, whose outer edge is curved ; upper surface of disk covered with small tuberculous 

 plates, forming a much raised rosette, the central plate of which is pentagonal, the 

 primary plates surrounding it semicircular. Radial shields closely soldered together, 

 and partly separated by an angular plate. In the interbrachial spaces are two large 

 plates, radiating from the central rosette, one five sided, with an acute angle inward, and 

 joined to the inner edge of the radial shields ; the other, which is on the margin of the 

 disk, is a large, nearly square, corrugated plate, and is attached on either side to small 

 oval plates, which form above the base of the arm two irregular transverse rows, three 



