348 PALAEONTOLOGY OF ILLINOIS. 



They further use the term "oro-anal side" for the upper truncate 

 regions of the body, and they include herein the ambulacra. 



It has been asserted by Mr. Lyon (Owen's Kentucky Eep. Vol. Ill, 

 p. 468), that in the genera Cadaster and Pentre mites the plates, gen- 

 erally known as basals, consisted of two successive series of pieces, 

 and upon this ground he proposed a new formula for the two genera. 

 Only to the "lower series" of plates he applied the term basals, the 

 "upper series" he called first radials. He explains the deficiency 

 from five to three in the number of the latter plates, and the irregu- 

 larity which he found in their form and position, compared with 

 other radials, that the two equal hexagonal pieces were perfect 

 plates, and the third smaller pentagonal one, imperfect. According 

 to his theory, there were no first radials in two of the rays, and the 

 rays commenced with a second radial. This curious interpretation 

 of the plates, as might be expected, found no followers, but his view 

 that in some of the Blastoids the plates formerly called basals were 

 composed of two series of three pieces each, was afterwards accepted 

 by Billings (Amer. Journ. Sci. and Arts, July, 1869), and also by 

 Meek and Worthen (Geol. Eep. 111., Vol. V, p. 464). The former 

 regarded the "lower pieces" as basals, the "upper ones" as sub- 

 radials ; while Meek and Worthen in redescribing Orophocrinus 

 (Codonites) stcllifonnis, 0. and Shum., distinguished the two series 

 as basals and supplementary basals, the latter to be applied to the 

 "lower series." They objected to the name subradials from the fact 

 that the plates do not alternate with each other. In the course of 

 their remarks they made the peculiar statement, that the lower 

 series or supplementary basals "were in adult specimens of Codonites 

 stelliformis as solid as we flnd them in Pentremites, young individuals, 

 however, show clearly that they are actually composed of Jive or six of 

 the upper joints of the column, enlarged and anchylosed together." 

 Meek and Worthen undertook to prove this by a moderately small 

 specimen, in which five or six joints of the column were preserved, 

 and in the same direction divided longitudinally into three sections. 

 It should be stated that the specimen, which was formerly in my 

 collection now in the Museum of Comparative Zoology at Cam- 

 bridge is not much below medium size, and, therefore, can not by 

 any means, be called a very young specimen. The column, as far 

 as preserved, consists as in most Blastoids of remarkably short 

 joints with sharp edges, and the joints are separated by rather deep 

 notches ; the longitudinal sutures are not shown distinctly, but prob- 

 ably do exist in the specimen. 



