NO. II ECHINODKRMS CLARK 9 



OPHIONEREIS ROOSEVELTI, n. sp. 



Plate 2, figs. 7, 8 



Characters. — The arms are black with well-separated small paired 

 spots, and, distally, bands of white ; the disk is brownish with numer- 

 ous small whitish spots in the outer portion and fine parallel radiating 

 whitish lines in the center ; beneath, the arms are gray and the disk 

 black ; the arm spines are 4 on the first dozen arm combs beyond the 

 edge of the disk, after which the uppermost is absent, so that there 

 are only 3 from this point to the arm tip ; the spines of the successive 

 arm combs are aligned in regular rows along the arm. 



Description. — In the larger of the two specimens, designated as the 

 type, the disk is 19 mm. in diameter and the arms are 130 mm. long. 



The entire aboral surface of the disk is covered with overlapping 

 scales which are largest about the radial shields and in the radial areas, 

 becoming much smaller in the center of the disk and in the interradial 

 areas. Most of these scales are entirely concealed by a thick epidermis. 

 Before the removal of the epidermis the only scales visible are the 

 following: A row of about 15 conspicuous light-colored scales runs 

 outward from the ends of the radial shields along the edge of the 

 aboral surface of the disk for about one-third the distance across the 

 interbrachial space. These scales, which imbricate toward the radial 

 shields, become small and irregular toward the outer end of the row. 

 In the angle between this row of scales and the radial shields, and 

 extending downward for some distance behind the radial shields, there 

 is a more or less obscured group of scales, with an indefinite border. 



At the base of the arms, beyond the disk, the arm spines are 4 in 

 number. All 4 spines are approximately of the same length. The 2 

 central spines are stout, slightly flattened, with abruptly truncated, 

 broadly rounded ends, the lower spine of each pair slightly curved 

 aborally. The uppermost spine is slightly more slender than the one 

 just below it, and more strongly flattened. The lowest spine is mark- 

 edly more slender and more tapering than the others. After the ninth 

 to twelfth arm comb beyond the edge of the disk (usually the tenth or 

 eleventh) the uppermost spine disappears, the combs from that point 

 onward to the tip of the arm consisting of 3 spines of approximately 

 the same length, of which the 2 uppermost are similar, stout and blunt, 

 and the lowest is more slender and more tapering. In the outer 

 portion of the arms the difference between the spines gradually dis- 

 appears so that in the terminal portion the combs are composed of 3 

 similar rather slender tapering spines. The spines on successive combs 

 are all at the same height so that the spines are aligned in regular rows 

 along the arm, first in 4 rows, later in 3. 



