CLARK: BRITTLE-STARS. 321 



4 mm. across the disk; the arms are 13-15 mm. long; the disk-scales 

 are remarkably large and distinct; the arms are faintly banded with 

 darker and lighter bluish gray and distally there are inconspicuous 

 whitish margins. The distinctness of this little species is fully con- 

 firmed by these Tobagoan specimens, none of the characters showing 

 any tendency to intergrade with 0. angulaia or the other West Indian 

 species. Although the type-locality for 0. brachyactis is the Tortugas, 

 I failed to find it among the hundreds of specimens of Ophiothrix which 

 I collected and examined there in June, 1917. 



Ophiothrix dirrhabdota, sp. nov. 

 dippa^duiTos = with two stripes, in reference to the markings on the arms. 



Plate 5, fig. 1. 



Holotijpe.— M. C. Z., 4,212 and 4 Parahjpes, M. C. Z., 3,987. 

 Philippine Islands: Mindoro, Port Galera, June, 1912. L. E. 

 Griffin coll. 



Disk, 5 mm. across; arms about 40 mm. long. Disk covered by a 

 skin completely hiding the scales and carrying numerous opaque, 

 thorny stumps and spinelets without regular arrangement. Radial 

 shields large, separated, triangular; exact outlines hidden by skin; 

 length about equal to two thirds radius of disk, and width about half 

 as much; between them is a series of thorny spinelets and on the 

 surface of each are half a dozen or more thorny stumps. Upper arm- 

 plates quadrilateral, about as long as wide or nearly so; proximal 

 margin shorter and straighter than distal which is quite convex; 

 lateral margins concave; broadly in contact. Interbrachial areas 

 below thickly covered with thorny stumps. Oral shields nearly 

 triangular but with an evident convexity on distal margin, wider 

 than long; madreporite larger and more nearly diamond-shape than 

 the others. Adoral plates rather large, triangular, barely meeting 

 within. Oral plates also rather large, with very large oral tentacle- 

 pores. Tooth-papillae, numerous and small. First under arm-plate 

 very small, rounded pentagonal, longer than wide; succeeding plates 

 quadrilateral with rounded corners; first three longer than wide, 

 but following twenty about as wide as long, remainder gradually 

 becoming longer than wide again; proximal margin of plate shorter 

 than distal, so lateral margins diverge a little distally; all under arm- 



