476 FRANK SPRINGER 



without anal or intcrbracial plates, and persisting in this simple form 

 from the Silurian to the Carboniferous, It now develops that 

 this is not true for the Silurian species. Liljevall, while making the 

 drawings for me above referred to upon specimens in the Museum 

 at Stockholm, called my attention to the fact that in all Gotland 

 Ichthyocrini the right posterior ray has an extra plate, just like 

 Temnocrinus tuherculalus . By cleaning the base of some specimens 

 so that the infrabasals could be seen, he was able to locate the right 

 posterior ray by its being in line with the small infrabasal. It was 

 in this ray that the extra plate was invariably found, smaller than 

 the radial, sometimes visible laterally and sometimes hidden by the 

 column. Here, evidently, was also the radianal in its primitive posi- 

 tion. I have much pleasure in according to Mr. Liljevall the credit 

 for this sagacious observation of a fact which had escaped the notice 

 of all of us. 



This at once suggested the idea that probably the same thing 

 would be found in the Silurian Ichthyocrini from England and 

 x\merica; and an examination of the published descriptions imme- 

 diately furnished abundant indications of it as to the American 

 species. Hall's figures and diagrams of /. laevis, ' and of /. simplex'' 

 show an extra plate in one ray. So also do his figure of /, suhan- 

 gularis,' and Ringueberg's figure and description of his /. conoideus^ 

 A similar condition was indicated in Weller's description of /. suh- 

 angularis,'' where he says the radials are "generally unequal," and 

 " costals two, rarely three, in each ray." In all of these there appeared 

 to be in one ray four primary plates, instead of three as in the others, 

 though in none of them was the position of the infrabasals accurately 

 shown, so as to determine which ray possessed the extra plate. 

 Indeed, without special preparation the infrabasals cannot often be 

 seen in this genus. Nevertheless, with the facts shown by the Swedish 

 specimens, there seemed no reason to doubt that the irregular ray 

 was here also the right posterior. 



1 Palceontology of New York, Vol. II, Plate 43, Figs. 2a and 2e. 



2 Ibid., Plate 46, Fig. le. 



.3 Twenty-eighth Report, New York State Cabinet of Natural History, Plate XVI, 

 Fig- 13- 



* Annals, New York Academy of Sciences, Vol. V, No. 6, p. 301. 

 5 Bulletin IV, Chicago Academy of Science, p. 146. 



