12 BULLETIN 64, UNITED STATES NATIONAL MUSEUM. 



transverse section a hexagonal form. They are also deficient in the superficial orna- 

 mental lines and pores as in the C. ornatus and meconideus; at least not the least 

 traces of these ornaments are visible upon the seven specimens in my collection. 



The figures of Miller and Gurley show a node in the center of each 

 radial rather than an angular elevation of its center, but this differ- 

 ence is too slight to be of specific value. 



Formation and locality. — In a recent paper by Pate and Bassler 

 [1008] the Brownsport limestone of Foerste is subdivided into the 

 Beech River, Bob, and Lobelville formations, and Oaryocrinus bul- 

 bulus is referred by them to the middle or Troostocrinus zone of the 

 Beech River formation. Decatur County, Tennessee. 



Cat. No. 30006, U.S.N.M. 



Class BLASTOIDEA" Say. 



Family PENTREMITID^ Etheridge and' Carpenter (emend 



Bather). 



Genus PENTREMITES Say. 



The following remarks are by Troost : 



The Genus Pentremites established by our countryman Thomas Say, and on which 

 I wrote a memoir (Trans, of the geol. Soc. of Penn. vol. I pag. 224.) is so well known 

 that it requires merely a short notice of how the several species differ from one 

 another; and as to my knowledge, no good figures have been published of the Amer- 

 ican Pentremites, I offer here accurate representations of the Pentremites that occur 

 in the State of Tennessee with which those that I have seen in the States of Missouri, 

 Illinois, Kentucky and Alabama correspond. 



Some of the species of this genus are very abundant in certain parts of the Western 

 States, while others are scarce. A division of the Carboniferous limestone is particu- 

 larly characterized by Pentremites. I possess a slab of such Pentremital limestone 

 which has a surface of about 236 square inches; on this surface are 120 Pentremites, of 

 all sizes, from 4/5 to 1/10 of an inch in length; and, judging from the sides of the slab, the 

 whole of it seems to be made up of an accumulation of these fossils. They, being 

 siliceous, have withstood the decomposing action of the atmosphere which has dis- 

 solved the limestone, so that the fossils stand out in prominent relief, some for more 

 than two thirds of their diameter. It contains few other fossils; on the whole slab I 

 find only one Terebratula, two other bivalves and CyaihophUla, so that these seas 

 must have swarmed at that period with Pentremites. 



Whether the species which I here describe must be considered as true species or 

 as mere varieties, I leave others to decide. I. only mention that the Pentremites 

 here described inhabited different localities; the pyriformis occupies the lowest 

 strata of the Carboniferous series. The globosus, florialis and the florialis elongata, 

 are found in a higher situation. In Alabama in some places the pentremitic stratum 

 is in contact with the coal. The P. cherockee is very rare; I found it only in one place 



a The Blastoidea of the Troost collection were referred to Dr. Gustav Hambach for 

 revision, and the results of his work appeared in the Trans. Acad. Sci. St. Louis, 

 XIII, pp. 1-67. As the specimens described by Troost are not in the possession of 

 the writer, with the exception of Nucleocrinus globosus, Doctor Hambach's work is 

 followed without change except in a return to names which appear to have priority 

 as noted in the text. The synonymy is also added by the present writer. 



