98 BULLETIN 76, UNITED STATES NATIONAL MUSEUM 



flattened truncate spines in an oblique series, the outer the heavier and longer. Its 

 extremity is shallowly grooved and sometimes slightly broadened, as on the proximal 

 part of ray. The inner spine is attached lower on the furrow face of the plate, is 

 abruptly tapered at base, thence is very slender; not expanded nor sulcate distally. 

 Outer spine, 6 mm.; inner, 5.5 mm. 



Mouth angle broad, not at all sunken, with two postoral pairs of adambulacral 

 plates in contact interradially. (PL 45, fig. 7.) In young specimens (pi. 44, fig. 4) 

 only the inner half of the first pair is in contact. The first adambulacral carries one 

 spine, the second, either one or two. Mouth plates with usually two, rarely three, 

 marginal spines and one long, slender, suboral spine. (PI. 45, figs. 6, 7.) 



Skeletal meshes large dorsally, but papulae are in small, spaced groups of from 3 

 to 10 papulae, there being from 2 to 6 of these groups in each mesh of the abactinal 

 skeleton. Intermarginal papulae in a single group of from 8 to 10 to a skeletal 

 interval, while actinally there are as many as 10 papulae proximally and only 1 or 2 

 distally (series extends 0.7 to 0.8 length of ray in large specimens). 



The thick circumspinal clusters of crossed pedicellariae in alcoholic specimens 

 nearly touch one another and form broad cushions marking the primary skeletal 

 plates. The pedicellariae are unusually large and are of a very characteristic form, 

 having two relatively large terminal fangs to each jaw with a row of three or four 

 prominent teeth below on the shank, the series ending with a group of four or five 

 denticles where the jaws cross. In a large specimen the pedicellaria is commonly 

 from 0.95 to 1.3 mm. long. (La Jolla; for other measurements see pi. 46.) An 

 attentive comparison of many of these pedicellariae has not revealed variations which 

 can be correlated with habitat. Almost the maximum variation is found in one speci- 

 men from Kell Bay, Alaska, (pi. 46. figs. 1, la, lb.) Very young specimens have 

 the characteristic pedicellaria, only much smaller. (Figs. 2, 2a.) 



Straight pedicellariae (pi. 45, figs. 1-4) are of the wedge-shaped, clawed type, 

 generally large (figs. 1, 2, 3) but sometimes predominantly small (figs. 3a, 4) the differ- 

 ence without apparent correlation to locality. These occur on the dorsal integument, 

 intermarginally and sparingly on the actinal plates, especially interradially. The 

 largest are 2.8 mm. long and are equally well developed in specimens from Alaska, 

 Monterey Bay, and off southern California. (Fig. 3). The smaller sort (figs, lb, 3a) 

 occur on the same specimens with the larger. Sometimes an example will occur 

 with only the smaller type. (Fig. 4, station 4552.) Small, broadly lanceolate, 

 acute pedicellariae sometimes occur sparingly on the furrow margin but are more often 

 entirely absent. 



Madreporic body large, circular, exposed; striae fine, radiating. 



Color in life from Monterey Bay examples: General tint of dorsal surface oliva- 

 ceous sepia; spines whitish. Integument between the thick tufts of pedicellariae, 

 deep brown, especially on disk, but little of this brown is visible on the rays on account 

 of the masses of pedicellariae. Actinal surface, buffy white. Occasional specimens 

 have the ground color dark bluish gray instead of brown. 



Variations. — These are comparatively slight considering the distribution in 

 latitude of the species. The difference in number of large and small straight pedi- 

 cellariae has already been mentioned. 



An example from station 4410 (pi. 48, fig. 1) is notable for the slender spines and 

 long slender rays (E=16 r), yet an example from station 4421 (pi. 49, fig. 2) from 



