20 BULLETIN 76, UNITED STATES NATIONAL MUSEUM 



Stegnobrisinga, Astrostephane), is dependent upon the number of rays, it may be 

 stated that A. acanthogenys with 11 rays has the plates as tightly joined as A. moluc- 

 cana, with 16 rays. In Brisingella, where this interradial pair of adambulacrals is 

 separated by the outer end of the combined mouth plates, so that they do not touch 

 by the lateral faces, the first marginal plates have a different relation also. With the 

 unpaired interradial plates they form an inverted Y, each arm being applied to the 

 upper edge of the first adambulacral plate, and the angle of the A being that of the 

 interradius. In Craterobrisinga alberti (Hawaiian Islands) which has nine rays (less 

 than Brisingella jragilis, type), the mouth plates do not separate the first or inter- 

 radial pair of adambulacrals as might be expected if the number of rays only deter- 

 mined the characteristic structure of the interradial angle of Brisingella. The proximal 

 part of the plates in alberti are normally joined, and the closely apposed first pair of 

 marginals has slipped down between the outer ends of the adambulacrals, cementing 

 firmly the ring of plates. There is no hint of the separation of the marginals to form 

 the A of Brisingella. 



This genus is not represented in the north Pacific region. A. moluccana was 

 taken in 265 to 559 fathoms in the Molucca Islands and Celebes; A. acanthogenys 

 was dredged in 172 fathoms, Lingayan Gulf, Luzon. 



Genus STEGNOBRISINGA Fisher 



Stegnobrisinga Fisher, New East Indian Starfishes, Proc. Biological Soc, Washington, 

 vol. 29, p. 33, Feb. 24, 1916 (subgenus). Type, Brisinga (Stegnobrisinga) placoderma 

 Fisher; Ann. and Mag. Nat. Hist., ser. 8, vol. 20, 1917, p. 428 (genus); Bull. U. S. Nat. 

 Mus. 100, vol. 3, 1919, p. 530. 



Diagnosis. — Resembling Brisinga in general appearance, and especially in 

 having definite transverse skeletal ridges, or costae, on the genital region, but differ- 

 ing in having the integument between the costal arches of ray strengthened by many 

 close-set, mostly contiguous or sometimes overlapping papery, spineless plates of 

 irregular form, completely filling the interspaces; in having two gonads to each ray. 

 Proximal subambulacral spines acicular; first adambulacral plate and first mar- 

 ginal plate joined for their whole length to the respective plates of adjacent ray; thus 

 there are four closely joined plates in each interradius; a nonmuscular symphysis, 

 or syzygy, between the first and second adambulacral plates and between the upper 

 parts of second and third ambulacral plates, as in Brisinga. 



Known only from a single species, S. placoderma, China Sea to Buton Strnit, 

 Celebes, 525 to 559 fathoms. 



Genus ASTROLIRUS Fisher 



Attrolirus Fisher, Ann. and Mag. Nat. Hist., ser. 8, vol. 20, 1917, pp. 424, 428. Type 

 Brisinga panamensis Ludwig; Fisher, Bull. U. S. Nat. Mus. 100, vol. 3, 1919, p. 504. 



Diagnosis. — Resembling Stegnobrisinga in the presence of spineless, immersed, 

 fenestrated thin plates in the intercostal integument, but differing in the structure of 

 the interbrachial angle, where the first pair of adambulacral plates are not joined 

 together by the interradial faces but are separate; first pair of marginal plates not 

 closely united by their interradial faces, but only by the adoral ends, to which also is 

 closely united the lower end of the interradial plate, forming a rude reversed Y of 



