NORTH PACIFIC OPHIURANS IN NATIONAL MUSEUM CLARK. 139 



joint. Tentacle pores on first arm joint very laro:e, protected by- 

 two scales; succeeding pores less conspicuous, protected by a single 

 large, oval scale. Color (dried from alcohol), light brown. 



Locality. — Albatross station? "No label in jar, Nov. 1892." 



Type.— C&t. No. 25638, U.S.N.M. 



This little specimen is doubtless still young, but the unusual com- 

 bination of six arms, short radial shields, elliptical upper arm plates, 

 long tetragonal under arm plates and four short arm spines distinguish 

 it from any other known Ophiactis. It is a great pity that there is no 

 clue to the locality of this interesting species. 



OPHIACTIS GYMNOCHORA, new species, a 



Disk 5 mm. in diameter; arms about 30 mm. long. Disk cov- 

 ered by about two hundred small scales, which, along the margin, 

 carry little spines. Radial shields long and narrow, separated witiiin 

 but in contact distally. Arms six, remarkably stout in proportion 



Fig. 54.— Ophiactis gymnochora. x 10. a, from above; 6, from below; c, -side view of three 



ARM joints near DISK. 



to the size of disk. Upper arm plates broadly hexagonal or heptag- 

 onal, much wider than long, in contact throughout; many are 

 broken into two or more pieces. Interbrachial spaces below quite 

 bare, save for scales alongside the genital slits, which are rather large. 

 Oral shields rounded without and pointed within, about as wide as 

 long. Adoral shields narrow within and much broader at outer 

 end, not meeting either radially or interradially. Oral piij)illce two 

 or three on a side, large, flat, rounded at tip. First inider arui plate 

 small, triangular; succeeding plates much larger, more or less octag- 

 onal, nearly or quite as long as wide, broadly in contact throughout. 

 Side arm plates rather small, not meeting either above or below; 



a ro/(vof, signifying naked, and x'^P"'> signifying space, in reference to the bare 

 interbrachial spaces. 



