NOETH AMERICAN PALAEONTOLOGY. 247 



Etheridge, Robert, Jr., and P. Herbert Carpenter— Coutinued. 



Dlwacrtnus, F. Roeuier, 1851 (Eiiieud. Hall, 186'2). Type Pentrcmitcs VerneiiiU, 

 Troost. This is purely .a Devouiau genus, aud appears to be geucrally dis- 

 tributed throughout that formation in the United States and Canada, but 

 is unknown in rocks of a similar age iu Europe. There appear to be no 

 species common to the Lower and Upper Devonian. Elceacrinus Vernenili, 

 xar. 2wmnm,.\a,r, nov., Columbus, Ohio; Corniferous limestone, Clarke 

 County, Indiana; Upper Helderberg group. Lower Devonian. 



Elceacrinus sp. ? 



II. Subfamily Schizohlaslidw, E. & C, 1886. 



Schisoblastus, E. & C, 1882. Type Fentremitcs Sayi, Shumanl. S. melonoides 

 and S. Saiji are limited to the Burlington group. These would be the earli- 

 est species of the genus, unless the Fenlremltes Saiiqisoni of Hambach form 

 the underlying Chouteau limestone, or Shumard's P. 2Iissouriensis should 

 prove to be a Schizohlastus. The authors know of no species of it above the 

 Burliugton limestone, with the possible exception of Granalocrbnts granu- 

 losus, M. & W., which occurs in the Keokuk limestone of Indiana aud Illi- 

 nois. Only four species are recognized as belonging certainly to this group, 

 though eight others, it is thought, may belong to it. 



Cryptohlastus, gen. nov. Type rentremites melo, Owen & Shumard. The genus 

 is exclusively confined to the Subcarboniferous of America, three species 

 belonging to the Burlington limestone and one to the St. Louis; but four 

 species are recognized. 



Granatohlasiidw, E. & C, 1886. Granuiocrinus (Troost, 1849; Hall, 1862) 

 (Emend. E. & C, 1882). Type rentremites Soricoodi, Owen & Shumard. 

 Of the sixteen species which have been described in America G. Nonvodi, 

 the type of the genus, is the only one which they can with any certainty 

 refer to this genus; it occurs in the Burlington limestone. The genus, as 

 now defined, is strictly limited to rocks of Carboniferous age. 



JHeterohlastus,* geu. nov. Type .ZZ". Cumherlandi, s-p. nor. 1 rentremites coriiutus, 

 M. & W., St. Louis limestone, is the only American species referred to this 

 genus. 



Codasteridw, E. & C, 1886. 



I. Subfamily riuenoschismidw, E. & C, 1886. 



Cadaster, McCoy, 1849. Type Cadaster irilohatus, McCoy. 



The authors are prepared to admit five or perhaps nine species of Cadaster 

 though not more, on account of the indefinite manner iu which certain so- 

 called Codasters have been described and figured. In Britain there is onlj^ 

 one C. irilohatus, the typo. The American species difier from the British 

 type iu possessing a more elongate form, greater convexity of summit, a 

 narrow base, and more complex ambulacra. Four of these are well defined, 

 viz : C. alternatus, C. gracilis, C. Uindei, aud C. 2^!/>'ii»iidatus. Doubtful 

 species are : C. Americanus, C. 2^Hlchellns, C. TVhitci, 'and railremiles suh- 

 truncatus. If C. ludchellus, Miller & Dyer, from the Niagara group be 

 rightly so uauied, this genus has the most extended geological range of all 

 the Blastoidea. Commencing iu the Upper Silurian of America, it is Avell 

 represented both in the Upper Helderberg aud iu the Hamilton group, of 

 the Devonian, especially the latter; while the doubtful C. Whitei, Hall, oc- 

 curs in the transition bed between the Upper Burliugton and the Keokuk 

 of the Subcarboniferous. The type species (C <ri/o&aii/s) is fairly abun- 

 dant in the Carboniferous limestone of Lancashire aud Yorkshire, and may 

 be considered, they suppose, as the last survivor of tho genus. 



* " Erfpof, unusual. 



