66 BULLETIN 76, UNITED STATES NATIONAL MUSEUM 



The bristling armature of the sides of ray, due to the vertical combs of marginal 

 spines is noticeable. (Stations 2850, 3214.) The less acervate examples of forma 



://,/ are near this subforma. 



The other Bubforma has less closely placed abactinal spmes, there are only one 

 or two superomarginal spines to a plate, and the straight pedicellariae are less heavy. 

 This variation resembles polythela with suppressed major spines. A specimen from 

 Kodiak 1ms one or two spinelets of the carinal series enlarged. Old Harbor, Kodiak; 

 Port Clarence. 



Type.— Cat. No. E 1491, U.S.N.M. 



Specimens examined— Type, station 2850, vicinity of Shumagin Islands, Alaska 

 (54° 52' N., 159° 46' W.), 21 fathoms, broken shells, bottom temperature 48.2° F., 

 one specimen. (PI. 25, figs. 2, 3.) 



Station 3214, South of Alaska Peninsula (54° 13' N., 163° 06' W.), 38 fathoms, 

 gray sand, gravel, one specimen. 



Old Harbor, Kodiak Island, August 11, 1888 (Albatross), one specimen. 



Port Clarence Bay, Alaska, 2 to 3 fathoms, Canadian arctic expedition. 



Forma ACERVATA (Stimpson) 



Plate 30, Figures 3, 3a-3/, 4, 4a; Plate 32, Figure 2, 2a-2c; Plate 37; Plate 38, Figure 1 



Asterias acervata Stimpson, 1862, p. 271. 



This is the forma to which the type specimen of Asterias acervata belongs (No. 

 1366, U.S.N.M.). The type, however, is an extreme rather than a mean of the forma, 

 being on the border toward polythela. Forma acervata represents a rather hetero- 

 geneous series of subformae connecting aphelonota with polythela and its type is 

 intermediate between average acervata (pi. 37, fig. 4) and typical polythela. The 

 forma may be characterized as follows: 



A large 6-rayed Leptasterias extremely variable in detail, but characterized by 

 having certain of the abactinal plates (often in three irregular series) larger than the 

 rest and armed with convex groups of coarse, capitate spines of which the central 

 spine is usually the largest; the ends of the spines subglobose to subcorneal, rather 

 finely striated; other abactinal spines well spaced, smaller, but similarly formed; 

 superomarginal spines one, two or even three to a plate, longer and slenderer, clavate 

 at times; inferomarginals similar, but heavier, one or two to a plate; one or two series 

 of actinal spines (one to a plate), similar to inferomarginals; adambulaeral spines 

 frequently alternating one and two ; furrow spine of alternate plates slenderer, tapering, 

 more advanced into furrow; consecutive plates with sometimes only one spine or 

 sometimes two; straight pedicellariae medium to large size, very broadly lanceolate 

 in profile, R = upward of 6 r. Largest specimen, R 154 mm., station 3496. 



Description. — Forma acervata is difficult to describe in other than rather general 

 terms because it is so unstable. The abactinal surface is especially inconstant to 

 stereotyped detail, although maintaining a recognizable facies. The spinulation of 

 the marginal plates is scarcely more uniform. All specimens which show a tendency 

 to have convex groups of slightly to conspicuously enlarged but subequal spines are 

 included herein, the extremes being well shown on Plate 37, Figures 1 to 4; Plate 38, 

 Figures 1,2. As mentioned above the actual type is intermediate between typical 



