ASTEROIDEA OF NORTH PACIFIC AND .VDJACENT WATERS — FISHEK. 249 



DERMASTERIAS IMBRICATA (Grubs). 

 PI. 49, figs. 1-2; pi. 56, ftg. 7. 



Aateropsis imhricata Grube, Archiv f. Naturgesch., 1857, p. 3-10; Xova Acta .\ca<J. Crca. Leop. 

 Carol. Nat. Cur., vol. 27, 1857, p. 6, pi. 1, fig. 5 (Sitka).— Verrill, Trans. Conn. Acad., vol! 

 1, pt. 2, 1867, p. 324.— A. Aoassiz, Mem. Mus. Comp. Zo61., vol. 5, No. 1, 1877, p. 106, pi. 15. 



Dermasterias inermis Perrier, R<5\-ision dcs Stcll<-ride*>, 1875, p. 282. 



Dcrmastcrias imhricata Sl.\dem, Challengrr .\.steroidea, 1889 (Vancouver Island to San Fran- 

 cisco).— Clahk, Proc. Boston Soc. Nat. IJist., vol. 29, No. 15, 1901, p. 325, pi. 1; pi. 4, figs. 

 2-4 (Puget Sound). 



"Dermastcr" imbricatus J. 1'". Whiteaves, Trans. Roy. Soc. Canada, vol. 4, sec. 4, 1886 (1887), 

 p. 117 (Melaspina Inlet, British Columbia and Johnstone Strait, British Columbia). 



Dia{inosis. —R&ys five. R=120 mm.; r = 45 mm.; R— 2.6 + r. Breadth of 

 ray at base, 50 mm. A small specimen: R = .55 mm.; r = 22 mm.; r = 2.5 imn. 

 Breadth of ray at base, 29 mm. Rays rather evenly tapered from broad base to 

 blunt extremity; disk usually fairly hi<i;h and abactinal surface more or less inflated 

 with interradial depressions; actinal surface flat. Whole animal covered with a 

 thick leathery membrane wholly obscuring the underlying plates, unless dried. 

 No spines excejjt ahmg furrow margin. Membrane contains flattened lime spicules 

 or deposits in the shape of rods or perforated plates. Papulae in areas, six or eight 

 longitudinal rows on each ray, anil upward to twenty-two papula? to an area; 

 large specimens usualh' with several (one to nine) small pedicellariffi on each area, 

 consisting of tw>, tlirec, or four granuliform jaws; pedicellariiv absent from smaU 

 and some large specimens. Marginal plates smooth, imbricated, numerous, nor- 

 mally wholly obscured by skin. Adambidacral plates with a stout blunt furrow 

 spine tipped with a soft fleshy knob, the whole scries along furrow margin being 

 connected by tough skin for about half the length of spines; back of these and 

 separated by a distinct furrow is a parallel ridge of tough skin not quite so high as 

 the furrow sj)ines, containing, for each plate, a flattened ovate or elliptical spinclet ; 

 the tips of these s])inelets give the ridge a scalloped appearance. In some large 

 specimens, in this furrow, between the two series of s])inules, at base of ray are a 

 number of j)odicellaria; with one, two, or three flattened ovate or elliptical jaws, 

 much larger than those of abactinal surface. Tube feet stout with largo sucking 

 disks, no deposits in wall. Madreporic bod}- flat, sunken in the abactinal skin; 

 striae fine, branching, radiating from an eccentric point. 



Description. — Grube (1857"), Agassiz (1S77), and Clark (1901) have figured 

 and described tliis species more or less completely. It will only be necessary, there- 

 fore, to enlarge upon certain features, as current descriptions need modification in 

 the light of more abundant material. 



The number of papuhe to an area is, of course, very variable, depemling chiefly 

 upon the size of the example. The areas are not always in very definite? or regular 

 series, but usually are. The jiedicellariai are jjresent in considerable numbers on 

 the abactinal surface <if all (seven) the large northern specimens, and also on two 

 medium-sized ones (Naha Bay). Two fairly large exami)les (Barclay Sound) have 

 only a verj' few pedicellariiv, and one (Barclay Sound), with K 73 nun., has none. 

 Small examples usually lack pedicellaria\ Specimens from the vicinity of Mon- 

 terej' Bay (one large and numerous medium-sized and small) lack pedioeflaria) 

 altogether. Tlie northern specimens, therefore, dilTer from the southern in usually 



