32 Pub. Fiiget Sound Biol. Sta. Vol. 2, No. 33 



stout. — Very scarce, in deep water. Not found by the writer, but reported 

 off Brown Island by Perry.* 



Genus Mediaster 

 Rays 5, rather long, tapered ; disk flat, broad. Dorsal plates rounded, 

 spinulose; marginal plates well developed, rather numerous, large, higher 

 than broad, paired series equal in size and number; actinal plates not 

 close, longitudinally arranged, elevated, roundisli, covered with spinules 

 or granules ; papulae single or clustered ; adambulacral plates with 1 

 regular marginal row of splender spines, 2 exterior longitudinal groups 

 of shorter spinules, similar to Ceramaster; pedicellariae sometimes lacking, 

 sometimes the actinal plates with single broad, sessile valvular pedicellariae. 



1. Mediaster aequalis Stimpson. 



Rays 5, variable in length, regularly tapered, slender at tip; disk, 

 medium; ratio 1:3. Dorsal ossicles and granules as for genus; marginal 

 plates large, higher than wide, granulated ; the plates of the 2 rows are 

 similar in size and shape, alternate, and form the margin of the disk and 

 rays ; abactinal areas wide at base ; plates in areas rounded, elevated, 

 spinulose, separated by papular pores in groups ; valvular pedicellariae 

 often in center of plate; actinal plates closely united, varying in size; 

 adambulacral plates, squarish, not large, with blunt spinules in marginal 

 row and shorter ones externally ; spinules varying in size. Madreporite 

 small, sunken. — Rather numerous, in deep water northeast of Brown Island. 



Family LUIDIIDAE 

 Genus Luidia 

 Rays 5 to 10, flat, flexible; disk small; paxillae columnar, lobate, 

 articulated at base, quadrate at surface and crowded in rows, or stellate; 

 upper marginal plates small, paxilliform, round; lower marginals spinose 

 and spinulose. transversely elongated ; adapibulacral plates separated by 

 grooves, bearing furrow-spines and ventral spines ; pedicellariae if present 

 forceps-like. 



1. Luidia foliolata Grube. 



Rays tapered to slender tips ; disk small. Paxillae varying in form, 

 crowded, forming longitudinal and transverse rows ; papular pores large, 

 alternating with paxillae; upper marginal plates similar to adjacent ones 

 and joined to lower marginals; lower marginals large and prominent, each 

 bearing 3 to 5 principal spines, varying in size ; peractinal row continuous 

 with lower marginals, each bearing a cluster of spinules ; adambulacral 

 plates with 1 inner spine and about 3 grouped on the actinal surface; a 

 few pedicellariae on ventral surface. — Rather numerous, in deep water. 



♦Perry, Edna M. Distribution of certain invertebrates on a restricted area of 

 sea bottom. Puget Sound Marine Sta. Pub 1:175-176. 1916. 



