30 BULLETIN "S, UNITED STATES NATIONAL MUSEUM. 



Cribriform organs large, always three. The median has about twenty-four 

 hmiellie, the lateral about twenty. Their structure does not appear to be different 

 from those of tenehrarius, althouffh there is more tendency for the plate-like spinelets 

 to remain independent. 



Adambulacral i)lates shaped as in tenebrarius and with two acicular skin- 

 covered spinelets on the marf^n. Of these one stands on the prominent adoral 

 entl of plate, the other a trifle shorter at about the middle of concaA-e margin or a 

 little nearer adoral end. The longest spinelet is about as long as plate; the other 

 is the homologue of the segmental papilla of E. crassus and E. tenebrarius. 



Mouth plates very prominent actinally, a little wider at outer end than in tene- 

 brarius. Armature consists of an odd acicular spiimle at inner end of combined 

 pair and along the free margin a series of two to five similar spinelets increasing 

 slightly in size toward first adambulacral. 



Actinal interradial areas about as in tenehrarius, but covered with spaced 

 skin-covered spinelets verj^ similar in character and size to those of abactinal sur- 

 face. These spinelets varj^ in length and are more numerous near the marginal 

 plates than in the inner angle. Intermediate plates extend to fourth inferomarginal. 

 At outer end of combined mouth plates the triangular end of the odontophore is 

 visible. The triangldar lower end of ambulacral ossicles is visible, as in tenebrarius, 

 between the inferomarginal and adambvdacral plates, forming a series extending 

 to tip of ray. 



Madreporic Ixxly large, about as wide as median cribriform organ to which it 

 is adjacent. 



Anat&mical notes. — No superarabulacral plates. Gonads interradial. Stomach 

 simple with two short pouches protruding into base of arm. No intestine; no 

 anus. There are no deposits in peristome, in the specimen examined. 



Type. — Will be deposited in U. S. National Museum. 



Type-locality. — Exact locality not stated; description based on specimens 

 from seven stations between lat. 14° 46' N. and lat. 0° .36' S., and long. 98° 40' W.; 

 region of the Gulf of Panama. 



Distrihution. — Bering Sea (south of Pribilof Islands) to Gulf of Panama and 

 vicinit}' of Galapagos Islands, 859 to 1 ,879 fathoms, soft mud and ooze and fine sand. 



Specimens examined. — Six from the following stations: 



2859, off Prince of Wales Island, Alaska, 1,569 fathoms, gray ooze, two speci- 

 mens. 



3075, off Washington, 859 fathoms, green mud, one specimen. 



3603, Bering Sea, between Pribilof and Umnak Islands, 1,771 fathoms, brown 

 ooze, three specimens. 



RemarltS. — The specimens agree w^ell with Ludwig's description and figures 

 of his PorceUanaster pacificus, which thus, like tenebrarius, has a wide distribution. 

 There are a few minor points of difference, as in the spinulation of the terminal plate, 

 but this is subject to variation. The nearly related i-icinus is insecurely separated 

 from pacificus. .Vmong the differences mentioned by Ludwig the only one of any 

 importance is the absence of actinal interradial spinelets. 



