FOSSILS OF THE BURLINGTON GROUP. 401 



however, are more liable to be removed by any accident than the five 

 larger, surrounding pieces, because the latter are more deeply inserted, 

 in order to permit the five rather large ambulacral canals extending 

 inward from the arm-bases to pass over them, or rather along the upper 

 side of the sutures between them, while these furrows pass in under the 

 pieces forming the center of the vault, which are consequently less firmly 

 fixed. 



As we have not had an opportunity to examine the original typical 

 specimens of C. planus, figured by PHILLIPS and AUSTIN, we of course 

 cannot assert positively that the vault of these types was constructed 

 like that of the Iowa species we have described, but we are strongly 

 inclined to believe such was really the case, and that the apparent cen- 

 tral opening was closed by vault pieces when the specimen was entire. 



Of the American species presenting, so far as known, the characters 

 of this genus as properly restricted, the following examples may be 

 mentioned, though the vault of only the first two of these species is yet 

 know'i to us, viz : C. mak-aceus. Hall, C. loicemis, Owen and Shumard, 

 C. ( PoteriocriniLs ) Barrisi, C. viminalis, C. lamellosus, C. divarwatus 

 and C. rotundatus, Hall; also C. Saffordi, and perhaps C. Farleyl, M. 

 and "NY., and C. rigidus, White. 



CYATHOCRRESTUS SCULPTILIS, Hall. 



PL 4, Fig. 5. 



Cyathocrinus sculptilis, HALL, Supp. Geol. of Iowa, p. 59. 

 (Burlington limestone, Burlington, Iowa. 



CYATHOCRIXITES FRAGILIS, M. and W. 



PI. 2, Fig. 14. 

 Cyathocrinitf* fragili*, MEEK and WORTHEN. Proceed. A.cad. Xat. Sci., Phila., 1868, p. 237. 



BODY subsphseroidal, a little oblique, rather regularly 

 rounded to the column below, from near the middle, and a 

 little contracted above, composed of remarkably thin plates. 

 Facet for the attachment of the column not excavated, and 

 very small. Base having the form of a very shallow, sub- 

 pentagonal basin ; basal pieces with a general subquadrangu- 

 lar form, but really pentagonal from the slight truncation of 

 their smaller inner ends at their connection with column. 

 Subradial pieces comparatively large, hexagonal, excepting 



