ASTEROIDEA OF NORTH PACIFIC AND ADJACENT WATERS FISHER 7 



a. 4 No papulae present either on disk or on rays; no visible abactinal skeleton on rays but embryonic 

 plates may be concealed in the thin integument; gonads unknown. 

 b l . Minute embryonic lattice plates are present in abactinal integument of ray; functional skeleton 

 of ray reduced to ambulacral and adambulacral plates; disk finely spinulate, a few spine- 

 lets extending upon ray; interbrachial skeleton resembling that of Brisingella, but the first 

 marginals unequal in size; first adambulacral plates entirely separated; adambulacral 

 armature very simple. Genotype, Hymenodiscus agassizi Perrier. -Hymenodiscus Perrier. 8 

 b-. Rays composed of ambulacral and adambulacral plates, and an abactinal integument devoid 

 of skeleton, but covered with numerous, relatively large pedicellariae arranged in trans- 

 verse bands. Disk not known. Genotype, Gymnobrisinga sarsii Studer. .Gymnobrisinga 



Studer." 

 Genus BRISINGA Asbj0rnsen 



Brisinga Asbj0rnsen, Fauna Litt. Norvegiae, 1856, andet hefte, p. 95. Type, B. endecacne- 

 mos Asbj0rnsen. — Fisher, Annals and Mag. Nat. Hist., ser. 8, vol. 20, 1917, pp. 421, 

 426; Bull. U. S. Nat. Mus., 100, vol. 3, 1919, p. 509. 



Diagnosis. — Brisingidae without papulae; with the abactinal skeleton of rays in 

 the form of transverse independent arches separated by intervals lacking plates 

 (except sometimes microscopic plates carrying minute prickles); with numerous 

 gonads forming a series along either side of each ray; with a syzygy or nonmuscular 

 symphysis between the first and second adambulacral plates, and between the upper 

 end of the second and third ambulacral plates; with a united pair of first adambulacral 

 plates, and first marginal plates in each interbrachial angle — four plates in all; with 

 the subambulacral spines of proximal plates acicular, unmodified; accessory subam- 

 bulacral spine if present on adoral half of plate. 



Remarks. — In B. trachydisca Fisher the distal ends of the first or united pair of 

 adambulacral plates of each interradius are wedged apart by the united first marginal 

 plates — or rather appear to be. In Sars's admirable monograph of Brisinga coronata, 

 two figures of B. endecacnemos (Sars, 1875, pi. 8, figs. 8 and 9) show that the first 

 adambulacral plates are not joined so closely as in Brisingenes, Astrostephane, or 

 Stegnobrisinga. But the structure of these interradially situated adambulacrals and 

 marginals is quite different from that of the same plates of Brisingella, as may be 

 readily determined by examining Plate 4, Figures 4 and 6, of the same work. These 

 figures show the structure of the plates in Brisingella coronata (G. O. Sars). 



No species of Brisinga are known to occur in the North Pacific region. 



Genus CRATEROBRISINGA Fisher 



Craterobrisinga Fisher (subgenus), New East Indian Starfishes, Proc. Biol. Soc, Washington, 

 vol. 29, p. 33, Feb. 24, 1916. Type, Brisinga panoyla Fisher; Ann. and Mag. Nat. Hist., 

 ser. 8, vol. 20, 1917, pp. 421, 426; Bull. U. S. Nat. Mus., 100, vol. 3, 1919, p. 512. 



Diagnosis. — Differing from typical Brisinga (which it resembles in appearance 

 and in the possession of serial gonads and of closely apposed first adambulacral and 

 first marginal plates of adjacent rays) in having proximally two subambulacral spines 

 of conspicuous size, the larger of which (and also sometimes the smaller) has an 

 enlarged, modified, capitate, often truncate tip. Costae usually numerous, and 

 genital region extended; first adambulacral plate, and sometimes the first 2.5, joined 



• See Fisher, Bull. U. S. Nat. Mus. 100, vol, 3, 1919, p. 502, footnote; Ann. and Mag. Nat. Hist., ser. 9, vol.2, 191S, p. 104 (flg.). 



