386 TRANS. OF THE ACAD. OP SCIENCE. 



PENTREMITES (continued). 



symnietricus, Hall, 1858. Geol. Iowa, vol. i., pt. 2, p. 694, pi. 25, 

 fig. 14. — Kas. — Kentucky. 



Tennesseese,* Troost, 1850. Proc. Amer. Assoc. Camb. Meet., p. 



60. — Tennessee. 

 Troosti, Shumard — Pentremites globosus, Troost. Monog. — Hall, 



1858. Geol. Iowa, vol. i., p. 695, pi. 25, fig. 17. (Not P. 



globosa, Say .J) — Kas. — Hardin Co., Illinois; Mt. Sano, 



Alabama. 



truncatus, Conrad, 1843. Proc. Acad. Nat. Sci. Phil., vol. i., p. 



334. — Arch.(V) — Edwardsville, Madison Co., Illinois. 

 Verneuili, v. Elseacrinus Verneuili. 

 Whitei, Hall, 1862. 15th Rep. Reg. State Cab. N. York, p. 150. 



— Ham. — Western New York. 

 Wortheni, Hall, 1858. Geol. Iowa, vol. i., pt. 2, p. 006, pi. 15, 



fig. 1. (Compare P. Uneatus, Shumard.) — Arch. — Keokuk, 



Iowa; Nauvoo, Illinois. 



PETRASTER, Billings, 1858. Canad. Org. Rem., Dec. iii., p. 79. 

 (?) antiqua — Asterias antiqua, Troost, 1835. Trans. Geol. Soc. 



Penn., vol. i., p. 232, pi. 10, fig. 9.— 7Y.— Davidson Co., 



Tennessee, 

 rigidus — Palccasterina rigidus, Billings, 1856. Geol. Rep. Can., 



p. 291. — Petr aster rigidus, 1858. Can. Org. Rem. Dec. iii., 



p. 80, pi. 10, fig. 3.— Tr.— Ottawa, Canada. 

 Wilberanus, Meek & Worthen, 1861. Proc Acad. Nat. Sci. Phil., 



p. 142.— 7V.(?) or H. R.G.— Oswego, Kendall Co., Illinois. 



PLATYCRINUS, Miller,t 1821. 

 aequalis. Hall, 1861. Des. New Crin., Prelim. Not., p. 17. — Enc. 

 — Burlington, Iowa. 



X The specimen upon which Mr. Say founded his Pentremites globosa 

 was brought from the vicinity of Bath, England, by Mr. Reubens 1 ' 

 It probably does not occur in American strata, and most likely belongs to 

 Granatocrinus or Elceacrinus. 



t The great GemiaPlatycrinus,as at present constituted, embraces more 

 than a hundred species, of which number nearly seventy are peculiar to 

 American strata. It is, howeVer, capable of being divided into several dis- 

 tinct groups, into which the species might be conveniently distributed. 



The Messrs. Austin in their Monograph on Fossil and Recent Crinoidea 

 proposed to separate the Genus into three divisions, based upon differen- 

 ces of structure in the superior part of the body. Those species with a 

 central, elongated proboscis such as PlaUjcrinus Icevis, they proposed to 

 arrange in one division; those with central, valvate, unobtrusive mouths 

 in another, under the generic name of Centrocrinus; and those with lateral 

 or subcentral mouths in a third, under the term Pleurocrirms. 



A fourth division was proposed by Dr. Troost, in 1850, for some remark- 

 ably depressed species from the glades of Decatur County, Tennessee, un- 

 der the name of Cupelloecrinus, in which the second series of radial pi 

 are rudimentary, occupy a small depression in the upper margin of the 

 large first radials, and are a non-brachial be: i 



I have received through the politeness of Mr. Meek a paper ,jnst pub- 

 lished by himself and A. H. "Worthen, entitled "Descriptions ofJNew Cri- 

 noidea, &c, from the Carboniferous Rocks of Illinois and the adjoining 

 States." in which the authors, adopting the suggestions of the Messrs. Aus- 

 ' Troost, divide the Genus into the following four sections: 



"1. Platycrinus (typical). — With the summit terminating in a more or 



