REVISION OF PALEOZOIC STELLEEOIDEA. 209 



In Heliaster the original number is five, and the new rays are not 

 as a rule disposed bilaterally (pp. 63-66). 



Verrill (1914) states that Heliaster and allied living forms strikingly 

 resemble nelianthaster oi the Devonic, "and may indicate a con- 

 tinuous descent from these ancient forms" (p. 13). He also says, "I 

 am inclined to beUeve that the increase in number of rays has been 

 due more to the advantage gained in holdhig their food securely, and 

 in opening bivalves, than for holding to the rocks, though both go 

 together" (p. 16). 



Genus PAL^^OSOLASTER Sturtz. 



Plate 31. 



Palaeosol aster Sturtz, Verh. nat. Ver. preuss. Rheinl., etc., vol. 56, 1900, pp. 



226-229, pi. 2, figs. 1-3. 

 Helianthaster Clarke (part), Bull. N.Y. State Mus., No. 121, 1908, p. 64, pi. 11. 



Generic characters. — Disk very large, with 27 to 29 rays in the 

 genotyjDe, Avhich project one-third their length beyond the disk. 

 Animal large, up to 190 mm. in greatest diameter. Disk and rays 

 without marginaUa. Length of rays 95 mm., width of rays 7 mm. 



Abactinal area decidedly and abundantly spinous and devoid of all 

 columns of plates. 



Actinally the great disk is also decidedly spinous. Rays slender, 

 with wide ambulacra; ambulacral plates very narrow, seemingly 

 alternating, but more probably opposite, [—-shaped, with large podial 

 openings in two rows in each ambulacrum. The rays are bounded 

 by narrow columns of small adambulacral ossicles that bear spines 

 on their outer sides. Mouth circular and very large. The nature of 

 the stout oral armature can not be made out, 



Madreporite actinal, placed near the mouth, interbrachial, very 

 large, striate, more or less oval, about 34 mm. in greatest width. 



The general aspect is said to be much like the living Solaster ajinis 

 Brandt. 



Genoholotyye. — P. gregoryi Sturtz (citations as above). Lower 

 Devonic of Bundenbach, Germany. Another species occurs at this 

 locality and a third is found in the Upper Devonic of New York. 



RemarTcs. — For present purposes we may state that Palseosolaster 

 has from 25 to 29 rays and that the ambulacraUa are arranged opposite 

 one another; the other Sturtz genera, Echinasterias, EcJdnodiscaster, 

 and EcMnostella, are so much like Palseosolaster that they may be 

 disregarded. 



Clarke recently erroneously referred another very well preserved 

 species of this genus to Helianthaster (H. roemeri Clarke), but it 

 plainly has no direct relationship with H. rhenanus. This is seen 

 in the greater disk, larger number of rays, decidedly actinal position 



