STARFISHES OF THE PHILIPPINE SEAS. 255 



boring plates. Ofton tliore are 2 rods sid? by side connecting con- 

 secutive plates of the carinal series. The lateral radial plates are 

 also lobed ; but distally the lobes become obsolete. The papular areas 

 include 4 longitudinal series of plates on either side of the median 

 radial plates, and the rods are present connecting these. The inter- 

 radial side of the fourth row is without rods, being joined rather 

 tightly to the interradial plates which are four-sided and closely joined. 

 The papulae are present on the center of disk, and the connecting 

 rods are found here also. The figure will give a better idea of the 

 exact form of the plates (see pi. 91. fig. 6), which are paralleled by 

 those of Mediaster. 



Type. — In the British Musemn. 



Type-locality. — Off Tablas Island, Philippine Group, 100-115 

 fathoms, green mud, Challenfier station 204. 



Distribution. — Philippine Islands to the Banda and Arafura Seas, 

 28 to 180 fathoms. 



Specimens examined. — Two, from the following stations: 



Station 5367. North coast Mindoro (Yerde Island Passage), 180 

 fathoms, sand. 



Station 5520. Mindanao Sea, off Point Tagolo, Mindanao, 102 

 fathoms, bottom temperature 61.3'^ F. 



Genus MEDIASTER Stimpson. 



Mediaster Stimpson. Boston .Toiirn. Xi>.l:. Hist., vul. fi. p. .580. — Fishek, 

 1911 r?, p. 196. Type, M. aequalis Stimpson. 



Medhtster is closely related to Iiosasfer, and is separated from it 

 by the presence of rudimentary superambulacral ossicles and by the 

 form of the ray. Several series of abactinal plates extend nearly to 

 the tip of the ray, the last 2 or 3 superomarginals being separated 

 by a single radial series. Occasionally the last few plates are in 

 contact mediall3% or more than 1 series reaches the terminnl plate. 

 Both genera have the internal supplementary abactinal plates and 

 the serially arranged gonads. Both genera have species with only 

 a few gonads to the series {Mediaster aequalis and Rosaster alex- 

 andri or R. nannus) and species with comparatively many {Mediaster 

 ornatus and Rosaster syTnholicus or R. mimicus). The internal ossi- 

 cles are slenderer and better developed in Mediaster, having a wider 

 distribution, in M. aequalis extending to the interradial septa. 



Mediaster aequalis has 3 rather large tufts in each series of gonads, 

 nearer the margin than in BI. ornatus; M. arcuatus has 6 tufts (in the 

 specimen dissected) ; 71/. hairdii has 6 tufts (in specimen dissected) ; 

 M. ornatus has 5 to 10 tufts. 



Mediaster is closely related to Nectria, an Australian genus. Nec- 

 tria differs from Mediaster in having calcified interbrachial septa, 

 suj)plementary, internal, actinal intermediate plates, relatively very 



