ASTEROIDEA OF NORTH PACIFIC AND ADJACENT WATERS — FISHER 151 



buttress from which a slight but tough membranous interbrachufl septum projects 

 into the lumen of the disk. The gonads are attached to the dorsolateral body wall. 

 well above the superomarginal plates, at a distance from the base of ray about equal 

 to minor radius. They have the usual branched structure. 



Type. Cat. No. E. 14'- >( .», U.S.N. M. Cotypes in zoological collection, Stanford 



University, and in the British Museum (Natural History). 



Type-locality— Mororan, Hokkaido, -Japan. Collected by D, S. Jordan and 



J. O. Snyder. 



Remarks. — Lysastrosoma is sufficiently close to Pycnopodia to be included in the 



Pycnopodiinae. 



The structure of the crossed pedicellariae is strikingly similar 01 in the two genera . 

 In Lysastrosoma the large inferomarginal spinal sheath envelops both spines, but 

 in Pycnopodia each spine has its sheath and a distinct mass of pedicellariae. The 

 difference in the size of the mouth plates is of course due in part to the crowding of 

 the rays in Pycnopodia but not entirely, since some polybrachiato forms— Corona ster 

 for example — avoid extreme compression of the oral plates. The line drawings 

 show the essential difference in the arrangement of marginal plates in specimens of 

 approximately equal size. (PI. 73, fig. 1, and pi. 79, fig. 1.) 



LYSASTROSOMA DESMIOKA Clark 



Plate 73, Figure 2; Plate 74; Plate 76 



Lysastrosoma desmiora Clark, Some Sea-Start from the Riksmuseum, Stockholm. Arkiv 

 for Zoologi, vol. 18 A, No. 8, p. 5, figs. 1 and 2. 



Diagnosis.— Rays five. R 92 mm. ; r 1 1 mm., R = S.3 + r; breadth of ray at base, 

 13 mm. Rays slender, gradually tapering, pointed; disk small; interbrachial angles 

 obtuse; integument thin, revealing the abactinal and marginal plates in the dried 

 specimen. Differing from L. anthosticta in having more numerous abactinal plates; 

 more strongly built marginal skeleton with intermediate secondary superomarginal 

 and inferomarginal ossicles throughout the ray; with much stronger secondary mar- 

 ginal ossicles, especially on proximal half of ray; with broader mouth plates and 

 much larger specialized first adambulacral plates; submicroscopic abactinal platelets 

 lacking, except a relatively few distally. 



Description.— The abactinal spines arc rather uniformly spaced 2 or 3 mm. apart 

 without serial order; eight or nine can be counted in a zigzag line across th i base of 

 ray. They arc tapered, stoutly acicular, with usually a slightly swollen, minutely 

 thorny tip. The longest are on the proximal half of ray (2 to 2.5 mm.) whence they 

 decrease in length and caliber on the disk (1.5 mm.) and toward the end of ra\ 

 the outer half of which they are less numerous. Each spiue is invested in a membrane 

 which is expanded distally and bears a terminal convex circular mass of pedicellariae, 

 for the latter form a subterminal thick wreath. This membrane is probably thick 

 and rather tough, as in alcoholic specimens of anthosticta. 



The abactinal plates from which the spines arise are easily seen in the dried 

 membrane, and have an irregular circular or lobed contour and average about 1.5 

 mm. broad. They are quite independent of one another, but each plate usually has 

 under one or more of its lobes a small platelet or sometimes two or three in scries. 



• The figures given by VerrOl, BheJlW^atet Starfishes of the N'nrili Pacll J, pi. 7», 0g. 6; i 



fi B . 7c for Pycnopodia arc unliko an} pedlcaUaiiae I have met with in thai sr»-cios. Some 61 the figures suggest Sfflotl 



