248 CATALOGUE OF THE BLASTOIDEA. 



These are always extreme forms of Var. A, and indicate a transition towards Grana- 

 tocrinus curtus, Shumard 1 . 



5th. In the degree and development of the ornament. The granular ridges are 

 much more numerous in some forms of Var. A than they are in others, either of 

 A or of B. 



6th. In the development of the short spiracular tubes (compare PI. II. figs. 32-35 ; 

 PL VII. figs. 3, 5, G). 



All these varietal forms, however, have certain very definite characters in common ; 

 e. g. the basal concavity, and the more or less tubular spiracles. We do not feel 

 therefore that there is any other course open to us than to retain them all under the 

 name G. Noriooodi. It is more than possible that the form Meek and Worthen 

 wished to separate under the name of G. jimbriatus 2 is only a well-marked variety 

 of G. Norwoodi. 



The other American Blastoids which may eventually prove to belong to Granato- 

 crinus are distinguishable from G. Norwoodi by well-defined characters. The horn- 

 like deltoid plates of G. 1 comutus, M. and W. 3 , are altogether absent in the former 

 type ; whilst the outline of the calyx in G. 1 curtus, Shumard 4 , at once separates that 

 species, notwithstanding the projecting radii of one variety of G. Norwoodi. Again, 

 the larger deltoids, and the ornament, of G. 1 granulatus, Koemer 5 , and G. 1 Boemeri, 

 Shumard 6 , together with the general outline of the calyx in G. 1 Shumardi, M. & 

 W., distinctly mark them as species which are separate both from one another and 

 from Granatocrinus Norwoodi. 



Localities and Horizon. Burlington, Iowa; Pleasant Grove, Iowa; near Monmouth, 

 Illinois. [Shumard also gives Hannibal and St. Louis Co., Missouri. Other 

 localities are Clarke Co. and Louisiana, Missouri] : Upper Burlington Limestone, 

 Subcarboniferous. 



Granatocrinus orbicularis, G. B. Sowerby, sp. 

 (PI. IX. figs. 11-16 ; PL XVII. fig. 5.) 



Pentatrematites orbicularis, G. B. Sby., Zool. Journ. 1835, vol. v. no. 20, p. 456, t. 33, 



Supp. f. 5. 

 Pentremites orbicularis, Phillips, Geol. York. 1836, pt. 2, p. 207, t. 3. f. 9. 

 Pentatrematites orbicularis, Roemer, Archiv f. Naturgesch. 1851, Jahrg. xvii. Bd. i. p. 363. 

 Pentremites orbicularis, Dujardin & Hupe, Hist. Nat, Zooph. Echinod. 1862, p. 95. 



1 Swallow's 1st and 2nd Report, Geol. Survey Missouri, 1855, p. 187, t. 13. f. 3, «, b. 



2 Proc. Acad. Nat. Sci. Philad. 1869, p. 258. 



3 Report Geol. Survey Illinois, 1866, vol. ii. p. 276, t. 20. f. 1 . 



4 Swallow's 1st and 2nd Report, Geol. Survey Missouri, 1855, p. 187, t. Ii. f. 3<t. 



5 Archiv f. Naturgesch. 1851, Jahrg. xvii. Ed. i. p. 363, t, 6. f. 13. 



6 Loc. at. t. B. f. 2 a ; Peport Geol. Survey Illinois, 1808, vol. iii. p. 498, t. IS. f. 6. 



