ASTEEOIDEA OF NORTH PACIFIC AND ADJACENT WATERS — FIBHEB. 



353 



Description. — Tliis form is evidently a northern representative of Pteranter 

 jordani, and wHthout careftd examination the two mij,'ht he easily confused. The 

 paxillar spines are not, however, so I<in^ as in jordani, altiioii^;!! tiie pseudopaxilla' 

 have tlie same cliaracter. Tiie spines are 7 or S mm. long, and one is commoidv 

 slenderer than the otlier two; pedicel ahoiit 1 to 1.25 mm. high. In the alcoholic 

 specimens the supradorsal membrane is smooth, fairly thick, and few spines pro- 

 trude through. At any rate, it has not a rough, swollen, or warty appearance. A 

 piece of the membrane cleared siiows in scattered places a few minute straight or 

 slightly curved, sometimes incii)iently branched, rods, wholly unlike the crowded 

 spiny deposits of miUtaris. Spiracles so few or inconspicuous that none can b^^ 

 detected. The supradorsal membrane is decidedly thicker than in jordani. ()scu- 

 lum as in jordani, each valve with about fourteen spines in two rows. 



Proximally the adambulacral plates have five long, slender spines heavily 

 sheathed and capped by a saccuhis, and imiteil by a membrane which joins the 

 actinolateral membrane usually beyond the end of the outermost spine. The outer 

 part of successive webs is joined by a slight horizontal membrane (not present in 

 jordani), which forms a sort of lateral cul-de-sac at the mouth of which is the 

 aperture and its papilla (similar to those of jordani). Kar along the ray each 

 comb has four spines; proximally the first spine is sometimes much shorter than 

 the second, sometimes nearly as long. On account of the four-ranked tulx* feet, 

 alternate adambulacral plates and armature are crowded back just a trifle. In 

 Diplopteraster this crowding is carried farther, and the alternate adambulacrals 

 iiave a less number of spinelets. 



Mouth plates similar in form to those of jordani; marginal spines five, united 

 by membrane, rapidly graduated in length from the long (10 mm.) inner to the 

 short (2.5 to 3 mm.) outer; suboral spine slender, as long or longer tiian inner 

 marginal, just behind wdiich it stands. 



Actinolateral membrane narrow and similar to that of jordani. 



Type.— C&t. No. 27791, U.S.N.M. 



Type-locality. — Albatross station 4784, near Attn Island, -Vleutians, 135 fath- 

 oms, coarse pebbles. 



Distribution. — Bering Sea, 52 to 351 fathoms, on gravel. 



Specimens examined. — Twenty, from the following stations: 

 Specimens of PterasUr marsippus examined. 



Depth. 



Nature of bottom. 



2842. 

 3223. 

 3486. 

 3330. 

 3500. 

 477». 

 4784. 

 47V2. 



Near Unaliukn. 



.do. 



West or Prlbilor Islands 



Near V imloakn 



South of I'ribllof Islands 



NeorSemL-wpochnol bland. Aleutians. 



Near Attu I.tlnnd, .VIoutians 



Near Bering Island, Commander Ii- 

 lands. 



pebbles 



black pebbles 



green mud, flne sand. . 



black mnd. mud 



fine gray sand, gravel. 



fine gravel 



coane pebbles 



pebble* 



V. S. Nat. Uus. 



Da 



Do. 



D& 



Da 

 Albatm; aot. 



Da 



Da 



<• Tvt-o alhen probably from thla itaUon; label loat dllttnc earUiqualn laot. 

 r,7.144*— Bull. 7»V— 11 23 



