170 PALAEONTOLOGY OF ILLINOIS. 



base, so as to give the body a slightly hexagonal outline as 

 seen from below. These prominences are also continued on 

 down upon the basal pieces, gradually becoming obsolete as 

 they converge towards the narrow lower extremity. Length, 

 to the summit of the first radial pieces, 1.28 inch; breadth, 

 about 1.16 inch; height of base, 0.58 inch; breadth of do., 

 0.76 inch. 



This species is so nearly like Diclwcrinus leevus, Hall (Sup. Geol. Report, 

 Iowa, part 2, p 83), that we were at one time inclined to think it might be- 

 long to the same species. A more careful comparison, however, with the origi- 

 nal specimen from which Prof. Hall's description and diagram were made out, 

 leads us to regard it as distinct. In the first place, the specimen under con- 

 sideration is much larger than that described by Prof. Hall, and differs in 

 having the second radials more deeply inserted into the upper margins of the 

 first. It likewise differs in the possession of obtuse ridge-like prominences 

 down the middle of the first radial and first anal plates. Again, its first anal 

 plate terminates in a mesial angle above, instead of being truncated, and a lit- 

 tle excavated in the middle. 



It is perhaps more nearly allied to D. intermedins, de Koninck and Lehon 

 (Crinoides Ter. Carb. Bclg., p. 150), though it differs in having deeper and 

 narrower sinuses in the upper margins of the first radials. It also differs in 

 having the upper extremities of the first radials and first anal plate more 

 incurved, and in the possession of an obtuse mesial prominence on each of 

 these plates. 



Locality and position: Burlington, Iowa, Burlington Limestone, of Lower 

 Carboniferous series. 



Genus PLATYCRINUS, Miller. 



Synon. — Aslropodium (sp.), Ure, 1793. Hist. Rutherglen. p. 326 ; (not Defrance, 1819.) 

 Nave Encrinite, Parkinson, 1811. Organic Remains, II, p. 223. 

 Platycrinites, Miller, 1821. Nat. Hist. Crinoidea; Schlot., 1823, Nachtr. Zur 



Petrefakt. Th., 1, 1822, and others. 

 Platycrinus, Agassiz, 1834. Mem. Soc. Sci. Nat. Neuch., l,p. 19*7, and others. 

 ? Warsupiocrinites, Phillips, 1839. Murch. Sil. Syst., p. 672. 

 Centrocrinus, Austin, 1843. Mongr. Recent and Foss. Crinoidea, p. 6. 

 Fleurocrinus, Austin, 1843. lb. 



Edwardsocrinus, d'Orbigny, 1850. Prodr. Palasont. Strat. 1, p. 157. 

 ? Cupellseocrinus, (Troost), Shumard, 1865. Cat. Palaeozoic Foss., part 1, Bch., 

 p. 361. 



