1885.1 NATURAL SCIENCES OF PHILADELPHIA. 325 



the secondary radials, as seen by the surface ridges, which bifur- 

 cate along the middle portions of the plates. The plates succeed- 

 ing them are still in a free state, and appear as arm-plates, but 

 actually form extensions of the calyx, being not as yet connected 

 by interradials and interaxillaries, as in the more adult specimens. 

 A diversity in the number of secondary radials cannot be con- 

 sidered of generic value, at least not in a form like Glyptocrinus, 

 in which, as Miller himself has shown us (Journ. Cincin. Soc, vol. 

 vi, PI. 11, fig. 1), the rays remain in an immature condition, more 

 or less, even in the adult. The specimens referred to Pycnocrinus 

 are so embryonic in their condition, that it would be speculation 

 for us to assert to what species they belong, and we have con- 

 cluded to leave them as doubtful species under Glyptocrinus. 



The species now referred by us to Glyptocrinus have round 

 columns, with the exception of Glyptocrinus Fomshelli, which 

 Miller thinks may prove to be a distinct generic form ; while those 

 referred to JReteocrinus, with probably one exception, have pen- 

 tagonal columns. 



The species which were referred in Europe to Glyptocrinus, 

 probably with the exception of Glyptocrinus basalis (?), belong 

 to different genera. That species was figured without discrip- 

 tion in Murchison's Siluria, p. 206, from a specimen with arms, 

 and came from the Caradoc limestone. In this specimen, the 

 plates of the calyx cannot be recognized, but the arms are those 

 of Glyptocrinus. In the type specimen of McCoy, in which only 

 the calyx is preserved, the interradials apparently touch the 

 basals, which, if true, would exclude it from Glyptocrinus. 



The specimens described by Nicholson and Etheridge, jun., 

 under the name of Glyptocr. globularis, from the Craighead lime- 

 stone and from Traive Glen. (Monogr. Silur. Foss. Girvan Distr. 

 in Ayshire, 1880, pp. 328-30, PI. 22, figs 9-11), probably belong 

 to Archseocrinus. They evidently had underbasals, for the inter- 

 radials rest upon the basals, and alternate with the first radial 

 plates. Neither can the arms, fig. 12, on the same plate, which 

 are composed of a double series of joints, be referred to Glyp- 

 tocrinus. 



We add the following species to our former list : 



(?) 1854. Glyptocrinus basalis McCoy, Synops. Palaeoz. Foss., p. 57, plate I D, fig. 

 4, 1859, Murchison's Silur., p. 206. — Caradoc limest. Montgomeryshire, 

 Great Britain. 



