MUSEUM OF COMPARATIVE ZOOLOGY. 237 



arm-plates about as long as broad, with a strong notch on their outer side and 

 a curve within; they are somewhat separated. Side arm-plates stout, not 

 projecting, and completely covering the space between upper and under 

 plates, so that the arm, without its spines, has a pretty regular, rounded form. 

 Upper arm- plates slightly broader than long; length to breadth, near the 

 disk, .•! :.7 : distinct, rather thick, of a much rounded diamond-shape, with 

 the outer side curved, and the two laterals converging inward nearly to a 

 point. Disk, above, densely beset with very short, minute stumps, each 

 bearing a crown of two, three, or rarely four, sharp, diverging prongs, each 

 stump about .4 nun. high, on the average. Below, the interbrachial spaces 

 are naked. Genital scales, at outer end of openings, very broad, and arching 

 partly over the arm. Seven rather short arm-spines flattened, not much 

 tapering; the longest with seven to nine rather strong thorns on each edge 

 and three blunt thorns at the tip ; the lowest has a hooked form even at the 

 base of arm. Lengths to that of an upper plate (7th joint) .8, 1.2, 1.2, 

 .5, .3, .2 : .6. Tentacle-scales minute, pointed. Color, in alcohol, pale blue, 

 with darker markings on upper arm. 



It differs from 0. pusilla in having the disk nearly or quite naked below, 

 in different upper arm-plates, and in wider arm-spines. 



Philippines, by Semper. Specimen also in Garden of Plants. 



Ophiothrix stelligera sp. nov. 



Plate III., Figs. 15 -SO. 



Special Marks. — Disk, above, closely beset with minute, stout stumps, 

 each with a crown of five or six short, not much diverging prongs ; there are 

 also a few short spines. Below, interbrachial spaces, near mouth, naked ; 

 but near edge of di<k, beset with small cylindrical spines. Under arm-plates 

 with a clean curve, without. 



Description of a Specimen. — Diameter of disk 5.5 mm. Length of arm 

 28 mm. Width of arm 1.5 mm. About twenty-one tooth-papillae, of which 

 fifteen form the border of the oval, and six are arranged in an irregular line 

 in the centre. .Mouth-shields as broad as Jong, of a rounded diamond-shape. 

 Underarm-plates a little broader than long; 7th plate, length to breadth, 

 .6 : .8, bounded, without, by a gentle curve, and by laterals which converge 

 moderately, giving the whole plate a nearly oval look. Side arm-plates only 

 moderately projecting, covering completely the space between the upper and 

 under plates. Upper arm-plates thickened and with a slight longitudinal 

 ridge; a little broader than long.; length to breadth .0 : .8, near di>k ; 

 bounded without by a curve; on the sides by re-entering curves, which con- 

 verge to a blunt point. Disk, above, closely beset with minute, stout stumps, 

 each with a crown of five or six short, not much diverging prongs ; the out- 



