130 BULLETIN 100, UNITED STATES NATIONAL MUSEUM. 



generally 2 series to each plate, that bordering the median suture 

 consisting of 10 to 14 short, stout, blunt, spinelets. The other or in- 

 termediate series is less regular and is composed of 8 or 10 shorter 

 spinelets. A third series continues the marginal series along the lat- 

 eral suture. That the teeth are occasionally broken in life is shown 

 by their absence on 2 mouth angles of the type, and by regenerating 

 members in 2 other angles. 



Madreporic body very convex, situated its own diameter nearer the 

 margin from the middle of r. 



Anatomical notes. — Intestinal coecum butterfly-shaped, the great- 

 est diameter about one-half r. Polian vesicles rather large with numer- 

 ous small diverticula scattered over the surface of the enlarged distal 

 portion. Superambulacral ossicles slender, and rather long, but ab- 

 sent from the first 3 ambulacral ossicles. The intermarginal pores, 

 described under P. euryactis hrevispinus, are w^ell developed, the 

 largest being the median interradial, which as seen from the coelomic 

 side has a diameter about one- third that of the plates adjacent. 

 From the outside, when the plates are carefully cleaned, the pore is 

 visible at the point where the transverse suture between a pair of 

 superomarginals meets the intermarginal suture (between the 2 

 series), but is covered with skin. There does not seem to be any 

 structure resembling a papula. The other pores are similar and de- 

 crease gradually in diameter, becoming very tiny at the middle of 

 ray, and soon ceasing. 



Type— Csit. No. 30526, U.S.N.M. 



Type-locality.— Station 5123, east coast Mindoro, 283 fathoms, 

 green mud ; 2 specimens. 



Distribution. — Known only from east of Masbate and east coast 

 of Mindoro, and neighboring waters, 283 to 604 fathoms. 



Specimens examined. — Six; 2 from type-locality and 4 from the 

 following stations: 



Station 5215, east of Masbate Island, 604 fathoms, green mud, bot- 

 tom temperature 50.5° F. ; 1 specimen. 



Station 5219, between Marinduque and Luzon, 530 fathoms, green 

 mud, sand ; 3 specimens. 



Remarks. — P. oediplojx differs from such species as euryactis^ an- 

 chistus, and luBonicvs in having much narrower and more tumid 

 superomarginals, each of w^hich bears a subcentral conical spine, not 

 an appressed spine or row^ ot spinelets near the distal border of the 

 plate. The three species mentioned are notable for their broad 

 inferomarginal plates also. P. oediplax differs from P. tenuis in 

 having much smaller and more tumid [armed] superomarginals and 

 less massive infcromarginals. The side of the ray of tenuis at base 

 is massive and high — higher than the actinal width of inferomar- 

 ginals— while in oediplao; the border of ray is equal to or less than 



