ASTEROIDEA i35 



A Study of the actual specimen, it need not be emphasized, provided the only means of 

 attacking a most baffling genus of a family noted for its taxonomic puzzles. 



Note on Cry aster brachyactis^ Clark. This species is known from 2 specimens 

 taken in 26 and 57 fathoms, Algoa Bay, South Africa. Dr H. L. Clark has kindly loaned 

 me the paratype. 



It is not a Perknaster for it has fairly large phanerozonid inferomarginal plates im- 

 bedded in the leathery body wall. These may bear, on the lateral face, a considerable 

 group of small spinelets and also sometimes a conspicuous flattened spine, several of 

 which are shown in the figure of the type. 



Another peculiarity is the great width of the adambulacral plates as compared to those 

 of Perknaster. The proximal plates commonly have 2 furrow spines in longiseries (in one 

 case, 3) and immediately behind these a larger subambulacral. The outer two-thirds of 

 plate is covered by skin only. Near the end of ray the spines form a transverse series of 

 2 or 3 or, rarely, 4 ; or sometimes only the furrow spine is present. When there is i furrow 

 spine its base is broad and occupies all the furrow margin of plate. 



Clark states that the "actinal intermediate areas are large, without calcareous plates, 

 spinules, or papulae". In the paratype there are well-marked large actinal plates in 

 irregular chevrons. A series adjacent to adambulacrals extends a little over half length of 

 inferomarginal series, the last plate being subequal to and opposite the sixth infero- 

 marginal. The remaining actinal interradial triangle is crossed by 3 to 5 irregular arcs 

 of plates, decreasing in size toward the margin and more and more separated as the 

 margin is approached. There are a few scattered small skin-covered spinelets which 

 disintegrate when treated with weak sodium hypochlorite. 



The abactinal plates have disappeared except for about a dozen at the tip of ray. 

 These are similar to the actinals, roundish or ovoid, some in contact, some isolated. 

 Also at the tip are a few remnants of the series of large superomarginals. They are 

 covered with very small, mostly degenerated, spinelets and their sacculi, which, after the 

 distal superomarginals are recognized, can be traced to the base of ray. Over most of the 

 ray the superomarginals have disappeared completely. 



The numerous, small, slender, tapered or clavate-acute, abactinal spinelets disintegrate 

 when treated with sodium hypochlorite although they show up plainly in a dried specimen. 



The madreporite is conspicuous, 3 mm. in diameter, and contiguous to its adcentral 

 border is an equally large primary interradial plate. 



This species, if its skeleton was complete, would have large roundish or slightly 

 lobed abactinal plates, perhaps connected by a few secondaries; large phanerozonid 

 superomarginals and inferomarginals ; large actinal plates in chevrons or arcs, and broad 

 but short adambulacrals. 



This is not Perknaster and probably Mortensen (1933, p. 249) is correct in assigning 

 Cry aster brachyactis and the nearly related '' Culcita'' veneris to the Asteropidae. I 

 might add: in the vicinity of Tylaster. Since Cryaster is strictly synonymous with 

 Perknaster it is not available for brachyactis which may therefore serve as the type of: 



1 Cryaster brachyactis H. L. Clark, 1923, p. 293, pi. n, figs, i, 2.— Mortensen, 1933, p. 249, pi. 12, fig. 14. 



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