196 



BULLETIN 76, UNITED STATES NATIONAL MUSEUM. 



The following apparentl}' constant clifTcrenccs separate the north Pacific species 

 from pectinifer, the larger specimen of which has II = 95 mm. (the same as Ludwig's 

 type from the Gulf of Panama): 



dissonus. 



Notably larger granules to the abactinal paxillae, 

 and fewer on surface of tabulum. 



Superomarginals at most one and one-half times 

 as wide as long; outer granules conspicuously 

 longer than inner, and one or more in the form of 

 short spinelets shaped something like a grain of 

 wheat ; other granules much fewer than in pectinifer, 

 and more or less elongate. 



Inferomarginal spinelets coarser and fewer. 



Actinal intermediate spinules shorter and 

 stouter. 



Postadambulacral pedicellarise bivalved, but 

 with sometimes a valvate pectinate form. 



Adambulacral plates proximally much longer 

 than wide, with tapering sharp furrow spinelets; 

 few actinal spinelets; intermediate plates and their 

 jjedicellariae (proximally) encroach upon adambu- 

 lacrals and sometimes push between them and 

 border the furrow. 



peclinifer. 



Granules of central portion of tabulum only half 

 as broad as thase in an equal-sized specimen of dis- 

 sonus. 



Superomaiginal plates at base of ray twice as 

 wide as long; granulation of even length, or only 

 one or two slightly enlarged granules near outer 

 end of plate; granules very short, truncate, or 

 slightly convex at tip. 



Inferomarginal spinelets slenderer and more 

 numerous. 



Actinal intermediate sjiinules slenderer and 

 longer. 



Postadambulacral pedicellariae pectinate only. 



Adambulacral plates proximally as wide or wider 

 than long, with truncate or blunt untapered furrow 

 spinelets; numerous actinal spinelets; intermedi- 

 ate plates and pedicellariae normally placed, not 

 encroaching upon adambulacrals and furrow mar- 

 gin. 



In pectinifer the adambulacrals are joined bj- their transverse margins, which 

 are well marked; ])ut in dissonus, as shown in the figures, there may be no true lateral 

 sutures between the plates, as the first row of intermediate plates encroaches upon 

 them. A portion of the inner edge of an intermediate thus comes to border the 

 furrow between two adjacent but partially separated adamliulacrals. There is no 

 hint of this in pectinifer, the surface of whose adambulacrals is much more spacious 

 and spiny. 



SubDniiily GONIA.STKR,IN"^E Verrill, XS99 (extendeci). 



Goniasterina'-\- Mediasterinx Veruill, Trans. Conn. Acad., vol. 10, 1899, p. 200. 

 Penlagonasterinx Sladen, Challenger Asteroidea, pp. xxxi, 262, 264. — Perrier, 1894, p. 337. 



Genus MEDIASTKR Stimpson. 



Medimtcr Stimpson, Boston Journ. Nat. Hist,, vol. 6, 1857, p. 530. Type, M. a;qualis Stimp- 

 son. — Sladen, Challenger Asteroidea,, 1889, p. 263. — Perrier, Exp^d. sci. du Travailleur et du 

 Talisman, 1894, p. 377; Result, camp. sci. du Prince de Monaco, fasc. 11, 1896, p. 45. — Ver- 

 rill, Trans. Conn. Acad., vol. 10, 1899, p. 178. 



Isaster Verrill (not of Desor), Proc. U. S. Nat. Mus., vol. 17, 1894, p. 257. Typo, Archcster 

 bairdii Verrill. 



Pemtagonaster Sladen (not Gray) part. Challenger Asteroidea, 1889, p. 277. 



Diagnosis. — Goniasteridse having a stellate form, with a broad flat disk, wide inter- 

 bracliial arcs and evenly tapered rays; with tabulate, regular more or less paxilliform 

 abactinal plates which meet the terminal plate in from one to three longitudinal 

 series; with internal radiating ossicles connecting the abactinal plates of papular 



