PALEONTOLOGY OF IOWA. 669 



CRINOIDEH OF THE ST. LOUIS LIMESTONE. 



I HAVE selected, from among the collections of Mr. WOR- 

 THEN, a few species from St. Louis for the illustration of this 

 formation, which, although occurring at numerous localities 

 and over wide areas in Iowa, has thus far afforded no fossils 

 of this family. 



These species of the Crinoideae of the St. Louis limestone 

 I originally arranged on the plates with those of the Keokuk 

 limestone, principally upon the authority of information 

 furnished by Mr. WORTHEN, which seemed to show that the 

 lower beds at St. Louis were on a parallel with the Keokuk 

 beds, and contained some of the same species of fossils ; and 

 the possession by Mr. WORTHEN of a (Melonites) Palechinus, 

 similar to the remarkable and characteristic one of St. Louis, 

 seemed to afford presumptive evidence of the identity of the 

 two limestones. Further examination, however, has not 

 shown any identical species ; and with my present informa- 

 tion, I must regard all the beds reached in the excavations 

 at St. Louis as pertaining to this division of the Carboniferous 

 limestone, as proposed by Professor SWALLOW. 



Poteriocrinus missouriensis. 



PLATE XVII. FIG. 7 a, b. 



Poteriocrinus longidactylus : SHTTMARD, Geological Report of Missouri, 1855, pa. 188, 



PU B, f . 5 a, b, c ( Non Austin Crinoid. pi. 11, f. 3) . 

 P. missouriensis : SHUMARD, Trans. Acad. Scien. St. Louis, 1857 (p. 12 of extract). 



BODY narrow turbinate, gradually tapering to the column 

 below. Basal plates five, pentagonal, length and breadth about 

 equal : subradial plates as wide as long, three regularly 

 hexagonal, two adjoining the anal side irregularly heptagonal. 

 First radial plates wider than long, alternating with the 



