220 Messrs. K. Etheridge, Jim., and P. H. Carpenter on 



oral ridge or abut against its sides. So far as we are able to 

 judge from the material at onr disposal, the American species 

 of Fentrennfes are all similar to P. Godoni, and readily recog- 

 nizable as belonging to this generic type as defined above. 

 In 1857 Mr. Sydney S. Lyon* announced the discovery in 

 certain species of Pentremites of three small pieces situated 

 below the basals, which he considered to represent the true 

 basals ; and heemended the formula of the genus accordingly. 

 This view was afterwards supported in part by Messrs. Meek 

 and Worthenf, wlio bore out Lyon's statement as to tlie pre- 

 sence of a dicyclic base in the calyx of Pentremites^ but re- 

 garded the lower series as supplementary basals rather than as 

 true basals. 



We have given great attention to this important question, 

 and must confess that up to the present time we liave quite 

 failed to detect any plates which could be regarded either as 

 supplemental or as under basals. We cannot help thinking 

 that the plates so regarded are nothing more than the upper- 

 most stem-joint more or less modified. Indeed it appears to 

 us that Messrs. Meek and Worthen were themselves not alto- 

 gether clear on the subject ; for in the description of their 

 figures of Oroifliocrinus {Codonites) sfeUiformi's, 0. & S.,tliey 

 say : — " Fig. 5, a. A side view of a small specimen, showing 

 the part under the base that has been, by some, supposed to 

 be in the Pentremites the true basal pieces, to be really only 

 some six of the upper joints of the column, anchylosed to- 

 gether and to the base " \. 



In the meantime we wish it to be distinctly understood that 

 we do not commit ourselves to either view, but leave the 

 question an open one for further consideration and investi- 

 gation. 



Genus Penteemitidea, d'Orbigny, 1849 

 (emend. E & C. 1882.) 



Pentremitidea, d'Orbigny, Prodrome de Pal. 1849, i. p. 102. 

 Pentremitidcea, d'Orbigny, Cours El^mentaire, &c. p. 139. 



Gen. char. Calyx varying in outline from elongately 

 clavate-pyramidal to pentagonal obpyriform ; summit trun- 

 cate or convex ; base usually long and conical. Number and 

 disposition of the plates similar to those of Pentremites proper, 

 but the orals inconspicuous, confined to the summit, and never 

 visible in a side view ; radial plates always strongly lobate. 



* D. D, Owen's ^rd Report Geol. Survey, Kentucky, 1857, p. 4G8. 

 t Illinois Geol. Survey Report, 187.3, v. p. 4G4 (note). 

 \ hoc. cit. V. expl. of pi, ix. fig. 5. 



