STARFISHES OF THE PHILIPPINE SEAS. 531 



STEGNOBRISINGA PLACODEBMA (Fisher). 



Plate 150 ; plate 153, figs. 2, 2a^d. 



DrisUuja (Stegnohrisinga) plaooderma Fishek, 1916&, p. 34. 

 Diagnosis. — Rays 13 or 14. Costae 35-40, close together, and not 

 very prominent ; the intercostal areas paved with close-set, irregular, 

 often overlapping, papery plates devoid of spinelets; costal arches 

 fairly regular and parallel, opposite every adambulacral, or occa- 

 sionally more frequent, but only every third to fifth with a lateral 

 spine; disk with beveled border and with close-set isolated spinelets 

 and conspicuous slender-jawed pedicellariae ; adambulacral armature 



variable ; in type usually — rr- or ^^^ ; sub ambulacra! spine equal 



to about 2^ or 3 adambulacral plates in length. Breadth of disk= 

 3|-4 times width of ray at base (8 mm.) ; actinostome=2| times 

 same; height of disk=seven-eights breadth of ray at base. R=370-}- 

 mm.j r=17 mm. (small portion missing from tip of ray). 



Description. — Disk moderately large, with a beveled border of 

 conspicuous width, the central area sunken a bit and plane. Plates 

 of disk small, subcircular, or irregular, and convex. Each plate 

 bears a single, central, sharp, tapering spinelet, which from being 

 sheathed in membrane has a papilliform appearance. These spine- 

 lets are about 0.5 mm. long and are spaced about their own length 

 apart. In the type about a third of the plates bear also a relatively 

 large slender- jawed pedicellaria, about as long as the spine, and 

 attached to the plate by a slender, short stem. In the cotype these 

 pedicellariae are nearly as numerous as the spinelets and are a 

 little larger than those of the type. 



Rays very long, swollen for a distance from base equal to a little 

 over twice diameter of disk. Costal region proper extending about 

 3 times diameter of disk from base, which is also about the extent 

 of the area paved with plates. This is less than a fourth the length 

 of ray, but none of the rays is quite complete. For a little over 

 twice the diameter of disk from base of ray the costae, 35 to 40 in 

 number, are close together and fairly regular, 1, occasionally 2, oppo- 

 site each adambulacral plate. The lateral spines occur only at the 

 ends of every third to fifth arch — that is, with 1 or 2 adambulacral 

 plates between them. The arches corresponding to the lateral spines 

 are more prominent than the others, especially laterally. Some of 

 the intermediate arches are rudimentary or incomplete in the mid- 

 dorsal region. The costal plates are irregularly elliptical or some- 

 times have short lateral lobes by which they are joined to the inter- 

 costal plates. Costal spinelets short, slender, tapering, sharp, all but 

 hidden in alcoholic specimens by the thick felting of slender- jawed 

 pedicellariae. The intercostal spaces are paved with thin overlap- 



