OPHIUROIDEA OF THE BAHAMA EXPEDITION. Ir 



Off Havana, no to 263 fathoms; also from 200 fathoms, 

 off Barbados, (Blake Exped.) Taken by the Blake Exped. 

 in 56 to 424 fathoms. 



A study of a series of specimens sent to me by Mr. Lyman 

 (from sta. 291, 200 fath., Blake Exp.) shows considerable 

 variation in the form of the oral shields. These are some- 

 times oblong, twice as long as broad, with the outer and inner 

 portions of the same width; in other cases the outer part, be- 

 yond the lateral indentations caused by the end of the genital 

 slit, is broader than the inner part; in other specimens the 

 outer part is narrower than the inner. The number and ar- 

 rangement of the large angular plates outside the oral shields 

 are variable even on the same specimen. Usually there are 

 three or four of the larger plates, of which two stand side by 

 side, near the margin of the disk. 



The radial shields are often separated distally by a row of 

 two or three small angular plates and a large proximal plate 

 as in our figure (pi. Ill, fig. 4), but in other specimens the 

 radial shields are in contact distally, but separated proximally 

 by a single large triangular plate, as in Mr. Lyman's type- 

 specimen. The central disk-plate is usually closely surround- 

 ed by five large angular plates, but in many cases there are 

 small plates intervening more or less irregularly. The varia- 

 tions in the scaling of the disk and in the radial shields are 

 not coincident with the variations of the oral shields. 



The varietel name is given to the variety with distinctly 

 separated radial shields, regardless of the variations in the 

 oral shields, which happen to be, in both the specimens fig- 

 ured, (pi. Ill, figs. 3 and 4) of the shorter and more ovate 

 form. 



This species is allied to O. tessellata. It is easily dis- 

 tinguished by the large, irregular disk-plates, wide, oblong, 

 oral shields; three subequal arm-spines, low down on the sides. 

 There are no marginal spinules outside the radial shields. 

 The upper arm-plates also differ in form. 



