ZOOLOGICAL HISTORY OF THE BLASTOIDBA. 6 



Pfuenoschisma, while the last, Pentremites crenulatus, Roetner, is the typo of 

 Mesoblastus, one of our latest genera. Four more species were described in L855 l » y 

 Shumard 1 , who was the first American author to use Roemer'a nomenclature; 

 while at the same time he brought forward some Important now evidence respecting 

 the closure of the summit-openings by additional plates, and three years later he 

 published some further observations upon the same subject 2 . 



The year 1856 witnessed the establishment by Shumard and Yandell 3 of another 

 new genus, Eleutherocrinus, for a very remarkable asymmetrical Blastoid from 

 Kentucky; and during the next few years a great number of new species of 

 Pentremites were described by Hall, Lyon, Shumard, Meek and Worthen, and 

 others. 



Some important descriptions of Elivtierhmx and Eteutherocrinus were published in 

 1862 by Prof. J. Hall ', who also proposed to use Troost's MS. name Granatoerinus 

 for species of the type of Pentremites Norwoodi, Owen and Shumard. 



During the next year some valuable observations on the closure of the summit 

 and ambulacra were published by Dr. C. A. White 5 , who also revived Say's theory 

 respecting the presence of tentacles on the ambulacra, although Roemer had pointed 

 out the difficulties involved in this view. 



The year 1S64 witnessed Von Seebach's proposal to make Pentremites stelliformis, 

 Owen and Shumard, the type of a new genus, Orophocrinus 6 ; and in the following 

 year were published the most important observations of Rofe 7 on the structure of 

 the hydrospires or subambulacral lamellar tubes in the British species of Granato- 

 crinus and Codaster, with his suggestion that they probably served a respiratory 

 function. About this time also Shumard 8 proposed to separate Pentremites Bein- 

 wardti and its allies under the generic name Troostocrinus. 



1 " Palaeontology '* in Swallow's First and Second Annual Beport, Geol. Survey Missouri, 1S55, pp. 185- 

 187. 



2 " Descriptions of new Species of Blastoidea from the Palaeozoic Rocks of the Western States, -with some 

 Observation- on the Structure of the Summit of the genus Pentremites." Trans. St. Louis Acad. Sci. L858, 

 vol. i. pt. 2, pp. 238-248, pi. 9. 



3 "Notice of a new Fossil Genus belonging to the Family Blastoidea, from the Devonian Strata near 

 Louisville, Kentucky." Proc. Acad. Nat. Sci. Philad. 1856, pp. 73-75, pi. ii. 



4 Fifteenth Annual Report, New York State Cabinet of Natural History (Albany, 1862), pp. 144-153. 



5 "Observations on the Summit-Structure oil Pentremites, the Structure and Arrangement of certain parts 

 of Crinoids, and Descriptions of New Species from the Carboniferous Rocks at Burlington, Iowa." Boston 

 Journ. Nat. Hist. L863, vol. vii. no. 4, pp. 481 -489. 



6 " Leber Orophocrinus, ein neues Crinoideengeschlecht aus dcr Abtheilung dor Blastoideen." Nae.hr. kgl. 

 Gcsellsch. Wissensch. zu Gottingen, 1864, pp. 110, 111. 



7 "Notes on some Echinodermata from the Mountain Limestone," &c. Geol. Mag. 186.3. vol. ii. pp. 2 1>- 

 251, pi. viii. 



8 " A Catalogue of the Pakeozoic Fossils of North America. — Part I. Palaeozoic Echinodermata." Trans. 

 St. Louis Acad. Sci. 1S65, vol. ii. no. 2, p. 384, note. 



